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.