Medicare is health insurance for the following:

People 65 or older
People under 65 with certain disabilities
People of any age with End-Stage Renal Disease (ESRD)

Medicare consists of 4 parts:

Medicare Part A (Hospital Insurance)

Helps cover inpatient care in hospitals
Helps cover skilled nursing facility, hospice, and home health care

Medicare Part B (Medical Insurance)

Helps cover doctors' services, hospital outpatient care, and home health care
Helps cover many preventative services to help maintain your health and to keep certain illnesses from getting worse

Medicare Part D (Prescription Drug Coverage)

A prescription drug option run by Medicare-approved private insurance companies
Helps cover the cost of prescription drugs
May help lower your prescription drug costs and help protect against higher costs in the future

Medicare Part C (Advantage Plan)

Plans offered by private insurance companies that contract with Medicare to provide you with all your Medicare Part A and Part B benefits. Medicare Advantage plans may also cover other services, including prescription drugs. Medicare Advantage plans have different structures and may be HMOs, PPOs or Private Fee-for-Service plans (PFFS). If you are enrolled in a Medicare Advantage plan, Medicare services are covered through the plan, and Original Medicare will not pay for any healthcare services received by an enrollee in a Medicare Advantage plan.

-OR-

Medigap Plan (Supplemental)

Medigap plans are supplemental insurance plans sold by private insurance companies to fill "gaps" in Original Medicare coverage. These plans are standardized across every carrier, meaning they must provide the same benefits. As of 2010, there are 11 available Medigap policies (A, B, C, D, F, high deductible F, G, K, L, M, and N). To qualify for enrollment in a Medigap policy, you must have Medicare Part A and Part B. Medigap policies only work in conjunction with the Original Medicare plan and will not pay for costs associated with Medicare Advantage. People in Medicare Advantage plans should not purchase Medigap policies. Below is a chart of the 11 available Medigap policies.