Medicare is a health insurance program for:
Part A Hospital Insurance - Most people don't pay a premium for Part A because they or a spouse already paid for it through their payroll taxes while working. Medicare Part A (Hospital Insurance) helps cover inpatient care in hospitals, including critical access hospitals, and skilled nursing facilities (not custodial or long-term care). It also helps cover hospice care and some home health care. Beneficiaries must meet certain conditions to get these benefits.
Part B Medical Insurance - Most people pay a monthly premium for Part B. Medicare Part B (Medical Insurance) helps cover doctors' services and outpatient care. It also covers some other medical services that Part A doesn't cover, such as some of the services of physical and occupational therapists, and some home health care. Part B helps pay for these covered services and supplies when they are medically necessary.
Prescription Drug Coverage - Most people will pay a monthly premium for this coverage. In January 1, 2006, Medicare prescription drug coverage became available to everyone with Medicare. This coverage is to help you lower prescription drug costs and help protect against higher costs in the future. Medicare Prescription Drug Coverage is insurance. Private companies provide the coverage. Beneficiaries choose the drug plan and pay a monthly premium. Like other insurance, if a beneficiary decides not to enroll in a drug plan when they are first eligible, they may pay a penalty if they choose to join later.
This information comes from www.cms.gov