Medicare is the federal health insurance program for people who are age 65 or older, certain younger people with disabilities, and people with End-Stage Renal Disease (permanent kidney failure requiring dialysis or a transplant, sometimes called ESRD).
The different parts of Medicare help cover specific services:
Medicare Part A (Hospital Insurance)
Part A covers inpatient hospital stays, care in a skilled nursing facility, hospice care, and some home health care.
Medicare Part B (Medical Insurance)
Part B covers certain doctors’ services, outpatient care, medical supplies, and preventive services.
Medicare Part C (Medicare Advantage Plans)
A Medicare Advantage Plan is a type of Medicare health plan offered by a private company that contracts with Medicare to provide you with all your Part A and Part B benefits. Medicare Advantage Plans include Health Maintenance Organizations, Preferred Provider Organizations, Private Fee-for-Service Plans, Special Needs Plans, and Medicare Medical Savings Account Plans. If you’re enrolled in a Medicare Advantage Plan, Medicare services are covered through the plan and aren’t paid for under Original Medicare. Most Medicare Advantage Plans offer prescription drug coverage.
Medicare Part D (prescription drug coverage)
Part D adds prescription drug coverage to Original Medicare, some Medicare Cost Plans, some Medicare Private-Fee-for-Service Plans, and Medicare Medical Savings Account Plans. These plans are offered by insurance companies and other private companies approved by Medicare. Medicare Advantage Plans may also offer prescription drug coverage that follows the same rules as Medicare Prescription Drug Plans.
Medigap (supplement insurance)
A Medicare supplement (Medigap) insurance, sold by private companies, can help pay some of the health care costs that Original Medicare doesn’t cover, like copayments, coinsurance, and deductibles. Some Medigap policies also offer coverage for services that Original Medicare doesn’t cover, like medical care when you travel outside the U.S. If you have Original Medicare (Part A and B) and you buy a Medigap policy, Medicare will pay its share of the Medicare-approved amount for covered health care costs. Then your Medigap policy pays its share. You can not be on a Medicare Advantage plan and buy Medigap insurance. You will also have to enroll in Medicare part D if you want prescription coverage.
Complete Medicare information at the official U.S. government Medicare site