In economics and law, insurance is a form of risk management primarily used to hedge against the risk of a contingent, uncertain loss. Insurance is defined as the equitable transfer of the risk of a loss, from one entity to another, in exchange for payment. An insurer is a company selling the insurance; an insured or policyholder is the person or entity buying the insurance policy. The insurance rate is a factor used to determine the amount to be charged for a certain amount of insurance coverage, called the premium. Risk management, the practice of appraising and controlling risk, has evolved as a discrete field of study and practice.

The transaction involves the insured assuming a guaranteed and known relatively small loss in the form of payment to the insurer in exchange for the insurer's promise to compensate (indemnify) the insured in the case of a large, possibly devastating loss. The insured receives a contract called the insurance policy which details the conditions and circumstances under which the insured will be compensated.
Risk which can be insured by private companies typically share seven common characteristics.

Large number of similar exposure units. Since insurance operates through pooling resources, the majority of insurance policies are provided for individual members of large classes, allowing insurers to benefit from the law of large numbers in which predicted losses are similar to the actual losses. Exceptions include Lloyd's of London, which is famous for insuring the life or health of actors, actresses and sports figures. However, all exposures will have particular differences, which may lead to different rates.

Definite Loss. The loss takes place at a known time, in a known place, and from a known cause. The classic example is death of an insured person on a life insurance policy. Fire, automobile accidents, and worker injuries may all easily meet this criterion. Other types of losses may only be definite in theory. Occupational disease, for instance, may involve prolonged exposure to injurious conditions where no specific time, place or cause is identifiable. Ideally, the time, place and cause of a loss should be clear enough that a reasonable person, with sufficient information, could objectively verify all three elements.

Accidental Loss. The event that constitutes the trigger of a claim should be fortuitous, or at least outside the control of the beneficiary of the insurance. The loss should be ‘pure,’ in the sense that it results from an event for which there is only the opportunity for cost. Events that contain speculative elements, such as ordinary business risks, are generally not considered insurable.

Large Loss. The size of the loss must be meaningful from the perspective of the insured. Insurance premiums need to cover both the expected cost of losses, plus the cost of issuing and administering the policy, adjusting losses, and supplying the capital needed to reasonably assure that the insurer will be able to pay claims. For small losses these latter costs may be several times the size of the expected cost of losses. There is little point in paying such costs unless the protection offered has real value to a buyer.

Affordable Premium. If the likelihood of an insured event is so high, or the cost of the event so large, that the resulting premium is large relative to the amount of protection offered, it is not likely that anyone will buy insurance, even if on offer. Further, as the accounting profession formally recognizes in financial accounting standards, the premium cannot be so large that there is not a reasonable chance of a significant loss to the insurer. If there is no such chance of loss, the transaction may have the form of insurance, but not the substance. (See the U.S. Financial Accounting Standards Board standard number 113)

Calculable Loss. There are two elements that must be at least estimable, if not formally calculable: the probability of loss, and the attendant cost. Probability of loss is generally an empirical exercise, while cost has more to do with the ability of a reasonable person in possession of a copy of the insurance policy and a proof of loss associated with a claim presented under that policy to make a reasonably definite and objective evaluation of the amount of the loss recoverable as a result of the claim.

Limited risk of catastrophically large losses. Insurable losses are ideally independent and non-catastrophic, meaning that the one losses do not happen all at once and individual losses are not severe enough to bankrupt the insurer; insurers may prefer to limit their exposure to a loss from a single event to some small portion of their capital base, on the order of 5 percent. Capital constrains insurers' ability to sell earthquake insurance as well as wind insurance in hurricane zones. In the U.S., flood risk is insured by the federal government. In commercial fire insurance it is possible to find single properties whose total exposed value is well in excess of any individual insurer’s capital constraint. Such properties are generally shared among several insurers, or are insured by a single insurer who syndicates the risk into the reinsurance market.

Insurance can have various effects on society through the way that it changes who bears the cost of losses and damage. It can increase fraud. On the other hand, it can help societies and individuals prepare for catastrophes and mitigate the effects of catastrophes on both households and societies.

Insurance can influence the probability of losses through moral hazard, insurance fraud, and preventive steps by the insurance company. Insurance scholars have typically used morale hazard to refer to the increased loss due to unintentional carelessness and moral hazard to refer to increased risk due to intentional carelessness or indifference. Insurers attempt to address carelessness through inspections, policy provisions requiring certain types of maintenance, and possible discounts for loss mitigation efforts. While in theory insurers could encourage investment in loss reduction, some commentators have argued that in practice insurers had historically not aggressively pursued loss control measures - particularly to prevent disaster losses such as hurricanes - because of concerns over rate reductions and legal battles. However, beginning around 1996 insurers began to take a more active role in loss mitigation through building codes.

Types of insurance
Any risk that can be quantified can potentially be insured. Specific kinds of risk that may give rise to claims are known as "perils". An insurance policy will set out in detail which perils are covered by the policy and which are not. Below are (non-exhaustive) lists of the many different types of insurance that exist. A single policy may cover risks in one or more of the categories set out below. For example, auto insurance would typically cover both property risk (covering the risk of theft or damage to the car) and liability risk (covering legal claims from causing an accident). A homeowner's insurance policy in the U.S. typically includes property insurance covering damage to the home and the owner's belongings, liability insurance covering certain legal claims against the owner, and even a small amount of coverage for medical expenses of guests who are injured on the owner's property.

Business insurance can be any kind of insurance that protects businesses against risks. Some principal subtypes of business insurance are (a) the various kinds of professional liability insurance, also called professional indemnity insurance, which are discussed below under that name; and (b) the business owner's policy (BOP), which bundles into one policy many of the kinds of coverage that a business owner needs, in a way analogous to how homeowners insurance bundles the coverages that a homeowner needs.

Auto insurance

A wrecked vehicleAuto insurance protects you against financial loss if you have an accident. It is a contract between the insured and the insurance company. You agree to pay the premium and the insurance company agrees to pay losses as defined in the policy. Auto insurance provides property, liability and medical coverage:

Property coverage pays for damage to or theft of the car.

Liability coverage pays for the legal responsibility to others for bodily injury or property damage.

Medical coverage pays for the cost of treating injuries, rehabilitation and sometimes lost wages and funeral expenses.

An auto insurance policy comprises six kinds of coverage. Most countries require you to buy some, but not all, of these coverages. If you're financing a car, the lender may also have requirements. Most auto policies are for six months to a year.

In the United States, the insurance company should notify you by mail when it’s time to renew the policy and to pay the premium.

Home insurance

Home insurance provides compensation for damage or destruction of a home from disasters. In some geographical areas, the standard insurances exclude certain types of disasters, such as flood and earthquakes, that require additional coverage. Maintenance-related problems are the homeowners' responsibility. The policy may include inventory, or this can be bought as a separate policy, especially for people who rent housing. In some countries, insurers offer a package which may include liability and legal responsibility for injuries and property damage caused by members of the household, including pets.

Health
Health insurance policies by the National Health Service in the United Kingdom (NHS) or other publicly-funded health programs will cover the cost of medical treatments. Dental insurance, like medical insurance, is coverage for individuals to protect them against dental costs. In the U.S., dental insurance is often part of an employer's benefits package, along with health insurance.
Health insurance, like other forms of insurance, is a form of collectivism by means of which people collectively pool their risk, in this case the risk of incurring medical expenses. The collective is usually publicly owned or else is organized on a non-profit basis for the members of the pool, though in some countries health insurance pools may also be managed by for-profit companies. It is sometimes used more broadly to include insurance covering disability or long-term nursing or custodial care needs. It may be provided through a government-sponsored social insurance program, or from private insurance companies. It may be purchased on a group basis (e.g., by a firm to cover its employees) or purchased by an individual. In each case, the covered groups or individuals pay premiums or taxes to help protect themselves from unexpected healthcare expenses. Similar benefits paying for medical expenses may also be provided through social welfare programs funded by the government.

By estimating the overall risk of healthcare expenses, a routine finance structure (such as a monthly premium or annual tax) can be developed, ensuring that money is available to pay for the healthcare benefits specified in the insurance agreement. The benefit is administered by a central organization such as a government agency, private business, or not-for-profit entity.

Life
Life insurance provides a monetary benefit to a decedent's family or other designated beneficiary, and may specifically provide for income to an insured person's family, burial, funeral and other final expenses. Life insurance policies often allow the option of having the proceeds paid to the beneficiary either in a lump sum cash payment or an annuity.

Annuities provide a stream of payments and are generally classified as insurance because they are issued by insurance companies and regulated as insurance and require the same kinds of actuarial and investment management expertise that life insurance requires. Annuities and pensions that pay a benefit for life are sometimes regarded as insurance against the possibility that a retiree will outlive his or her financial resources. In that sense, they are the complement of life insurance and, from an underwriting perspective, are the mirror image of life insurance.
In the U.S. an annuity contract is created when an individual gives a life insurance company money which may grow on a tax-deferred basis and then can be distributed back to the owner in several ways. The defining characteristic of all annuity contracts is the option for a guaranteed distribution of income until the death of the person or persons named in the contract. However, the majority of modern annuity customers use annuities only to accumulate funds and to take lump-sum withdrawals without using the guaranteed-income-for-life feature.

Annuity contracts in the United States are defined by the Internal Revenue Code and regulated by the individual states. Variable annuities have features of both life insurance and investment products. In the U.S., annuity contracts may be issued only by life insurance companies, although private annuity contracts may be arranged between donors to non-profits to reduce taxes. Insurance companies are regulated by the states, so contracts or options that may be available in some states may not be available in others. Their federal tax treatment, however, is governed by the Internal Revenue Code. Variable annuities are regulated by the Securities and Exchange Commission and the sale of variable annuities is overseen by FINRA (the largest non-governmental regulator for all securities firms doing business in the United States).

There are two possible phases for an annuity, one phase in which the customer deposits and accumulates money into an account (the deferral phase), and another phase in which customers receive payments for some period of time (the annuity or income phase). During this latter phase, the insurance company makes income payments that may be set for a stated period of time, such as five years, or continue until the death of the customer(s) (the "annuitant(s)") named in the contract. Annuitization over a lifetime can have a death benefit guarantee over a certain period of time, such as ten years. Annuity contracts with a deferral phase always have an annuity phase and are called deferred annuities. An annuity contract may also be structured so that it has only the annuity phase; such a contract is called an immediate annuity.

Certain life insurance contracts accumulate cash values, which may be taken by the insured if the policy is surrendered or which may be borrowed against. Some policies, such as annuities and endowment policies, are financial instruments to accumulate or liquidate wealth when it is needed.

In many countries, such as the U.S. and the UK, the tax law provides that the interest on this cash value is not taxable under certain circumstances. This leads to widespread use of life insurance as a tax-efficient method of saving as well as protection in the event of early death.

In U.S., the tax on interest income on life insurance policies and annuities is generally deferred. However, in some cases the benefit derived from tax deferral may be offset by a low return. This depends upon the insuring company, the type of policy and other variables (mortality, market return, etc.). Moreover, other income tax saving vehicles (e.g., IRAs, 401(k) plans, Roth IRAs) may be better alternatives for value accumulation.

Property
Property insurance provides protection against risks to property, such as fire, theft or weather damage. This includes specialized forms of insurance such as fire insurance, flood insurance, earthquake insurance, home insurance, inland marine insurance or boiler insurance.

Automobile insurance, known in the UK as motor insurance, is probably the most common form of insurance and may cover both legal liability claims against the driver and loss of or damage to the insured's vehicle itself. Throughout the United States an auto insurance policy is required to legally operate a motor vehicle on public roads. In some jurisdictions, bodily injury compensation for automobile accident victims has been changed to a no-fault system, which reduces or eliminates the ability to sue for compensation but provides automatic eligibility for benefits. Credit card companies insure against damage on rented cars.

Driving School Insurance provides cover for any authorized driver whilst undergoing tuition, cover also unlike other motor policies provides cover for instructor liability where both the pupil and driving instructor are equally liable in the event of a claim.
Aviation insurance insures against hull, spares, deductibles, hull wear and liability risks.
Boiler insurance (also known as boiler and machinery insurance or equipment breakdown insurance) insures against accidental physical damage to equipment or machinery.

Builder's risk insurance insures against the risk of physical loss or damage to property during construction. Builder's risk insurance is typically written on an "all risk" basis covering damage due to any cause (including the negligence of the insured) not otherwise expressly excluded. Builder's risk insurance is coverage that protects a person's or organization's insurable interest in materials, fixtures and/or equipment being used in the construction or renovation of a building or structure should those items sustain physical loss or damage from a covered cause.

Crop insurance "Farmers use crop insurance to reduce or manage various risks associated with growing crops. Such risks include crop loss or damage caused by weather, hail, drought, frost damage, insects, or disease, for instance."

Earthquake insurance is a form of property insurance that pays the policyholder in the event of an earthquake that causes damage to the property. Most ordinary homeowners insurance policies do not cover earthquake damage. Most earthquake insurance policies feature a high deductible. Rates depend on location and the probability of an earthquake, as well as the construction of the home.
A fidelity bond is a form of casualty insurance that covers policyholders for losses that they incur as a result of fraudulent acts by specified individuals. It usually insures a business for losses caused by the dishonest acts of its employees.

Flood insurance protects against property loss due to flooding. Many insurers in the U.S. do not provide flood insurance in some portions of the country. In response to this, the federal government created the National Flood Insurance Program which serves as the insurer of last resort.

Home insurance, also commonly called hazard insurance or homeowners insurance (often abbreviated in the real estate industry as HOI), is the type of property insurance that covers private homes.
Landlord insurance covers residential and commercial properties which are rented to others. Most homeowner's insurance covers only owner-occupied homes.

Marine insurance and marine cargo insurance cover the loss or damage of ships at sea or on inland waterways, and of cargo in transit, regardless of the method of transit. When the owner of the cargo and the carrier are separate corporations, marine cargo insurance typically compensates the owner of cargo for losses sustained from fire, shipwreck, etc., but excludes losses that can be recovered from the carrier or the carrier's insurance. Many marine insurance underwriters will include "time element" coverage in such policies, which extends the indemnity to cover loss of profit and other business expenses attributable to the delay caused by a covered loss.

Surety bond insurance is a three party insurance guaranteeing the performance of the principal.
Terrorism insurance provides protection against any loss or damage caused by terrorist activities.
Volcano insurance is an insurance that covers volcano damage in Hawaii.
Windstorm insurance is an insurance covering the damage that can be caused by hurricanes and tropical cyclones.

Credit
Credit insurance repays some or all of a loan when certain things happen to the borrower such as unemployment, disability, or death.
Mortgage insurance insures the lender against default by the borrower. Mortgage insurance is a form of credit insurance, although the name credit insurance more often is used to refer to policies that cover other kinds of debt.

Many credit cards offer payment protection plans which are a form of credit insurance.

Credit insurance is a term used to describe both business credit insurance (a.k.a. trade credit insurance) and consumer credit insurance, e.g., credit life insurance, credit disability insurance (a.k.a. credit accident and health insurance), and credit unemployment insurance.

The easy way to differentiate between these two types of insurance is:

- Business credit insurance is credit insurance that businesses purchase to insure payment of credit extended by the business.
- Consumer credit insurance is credit insurance that consumers purchase to insure payment of credit extended to the consumer.

Consumer credit insurance is a way for consumers to insure repayment of loans even if the borrower dies, becomes disabled, or loses a job. Consumer credit insurance can be purchased to insure all kinds of consumer loans including auto loans, credit card debt, short-term loans (payday), loans from finance companies, and home mortgage borrowing. Although purchased by the consumer/borrower, the benefit payment goes to the company financing the purchase or extending the credit to the consumer.

Credit insurance or trade credit insurance (also known as business credit insurance) is an insurance policy and risk management product that covers the payment risk resulting from the delivery of goods or services. Trade credit insurance usually covers a portfolio of buyers and pays an agreed percentage of an invoice or receivable that remains unpaid as a result of protracted default, insolvency or bankruptcy. Trade credit insurance is purchased by business entities to insure their accounts receivable from loss due to the insolvency of the debtors. This product is not available to individuals.

Mortgage insurance (also known as mortgage guaranty) is an insurance policy which compensates lenders or investors for losses due to the default of a mortgage loan. Mortgage insurance can be either public or private depending upon the insurer. The policy is also known as a mortgage indemnity guarantee (MIG), particularly in the UK.

For example, Mr. Bush decides to purchase a house which costs $150,000. He pays 10% ($15,000) down payment and takes out a $135,000 ($150,000-$15,000) mortgage. Lenders will often require mortgage insurance for mortgage loans which exceed 80% (the typical cut-off) of the property's sale price. Because of his limited equity, the lender requires that Mr. Bush pay for mortgage insurance that protects the lender against his default. The lender then requires the mortgage insurer to provide insurance coverage at, for example, 25% of the 135,000, or $33,750, leaving the lender with an exposure of $101,250. The mortgage insurer will charge a premium for this coverage, which may be paid by either the borrower or the lender. If the borrower defaults and the property is sold at a loss, the insurer will cover the first $33,750 of losses. Coverages offered by mortgage insurers can vary from 20% to 50% and higher.

To obtain public mortgage insurance from the Federal Housing Administration, Mr. Bush must pay a mortgage insurance premium (MIP) equal to 1.75 percent of the loan amount at closing. This premium is normally financed by the lender and paid to FHA on the borrower's behalf. Depending on the loan-to-value ratio, there may be a monthly premium as well. The United States Veterans Administration also offers insurance on mortgages.