Health insurance or medical insurance is a type of insurance that covers the whole or a part of the risk of a person incurring medical expenses. As with other types of insurance, risk is shared among many individuals. By estimating the overall risk of health risk and health system expenses over the risk pool, an insurer can develop a routine finance structure, such as a monthly premium or payroll tax, to provide the money to pay for the health care 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.