Medicare offers four kinds of insurance:

Source: Centers for Medicare and Medicaid Services

Medicare is health insurance offered by the federal government to most people who are 65 and older and to some younger people with disabilities.

Hospital insurance, called Medicare Part A, helps pay for hospital bills

When you sign up for Medicare, you automatically get Part A, which covers hospital bills. Most people do not have to pay a monthly cost (premium) for Part A, because they or their spouse paid Medicare taxes while they were working.

Part A covers inpatient hospital services (i.e., costs associated with an overnight stay in a hospital, skilled nursing facility, or psychiatric hospital, such as charges for the hospital room, meals, and nursing services). Part A also covers hospice care and home health care.

Medical insurance, called Medicare Part B, helps pay for doctor bills

You choose whether to enroll in Part B or not. You pay a monthly premium for Part B.

Part B covers physician care -- whether received as an inpatient at a hospital or at a doctor's office, or as an outpatient at a hospital or other health care facility -- as well as laboratory tests, physical therapy or rehabilitation services, ambulance service, diabetes supplies, flu shots, and some medical equipment.

Medicare Advantage (formerly Medicare+Choice), called Medicare Part C, adds more types of coverage

Medicare Part C programs are in addition to the fee-for-service options available under Medicare Parts A and B. Private health care plans may offer Medicare benefits that include medical savings accounts, managed care plans, and private fee-for-service plans.

Medicare Part C (Medicare Advantage Plans) is offered by government-approved private insurance companies and provides an alternative option. It combines Parts A and B. Some plans also include Part D coverage (MAPD plans) and some do not (MA plans). Costs vary by plan.

Prescription drug insurance, called Medicare Part D, helps pay for prescribed medications

Anyone who is eligible for Medicare is also eligible for Part D. As with Parts B and C, you have the choice to enroll or not, and you will pay a monthly premium. Medicare Part D benefits began January 1, 2006.

Medicare Part D (Prescription Drug Coverage) is offered by government-approved private insurance companies, and helps cover prescription drugs. This coverage is available as a prescription drug plan (PDP) if you have an Original Medicare Plan and is included in some Medicare Advantage plans (MAPD). Costs vary by plan.