Medicare is a national social insurance program, administered by the U.S. federal government since 1965, that guarantees access to health insurance for Americans ages 65 and older and younger people with disabilities as well as people with end stage renal disease. As a social insurance program, Medicare spreads the financial risk associated with illness across society to protect everyone, and thus has a somewhat different social role from for-profit private insurers, which manage their risk portfolio to maximize profitability by denying claims.[1]
This has helped improve the health and longevity of older Americans.[2]
[1] Wikipedia: Medicare
[2] National Academy of Social Insurance