Medicare is the Federal health insurance program for Americans age 65 and older and for certain disabled Americans. If you are eligible for Social Security or Railroad Retirement benefits and are age 65, you and your spouse automatically qualify for Medicare.
Medicare has three parts: hospital insurance (Part A), payments for doctors and related services and supplies ordered by the doctor (Part B), and prescription drug coverage (Part D). If you are eligible for Medicare, Part A is a free benefit of Social Security, but you must pay a premium for Part B and Part D.
The best source of information on the Medicare program is the Medicare Handbook. Find this book at  www.medicare.gov or your Social Security office.

Some people who are covered by Medicare buy private insurance, called "Medigap" policies, to pay the medical bills that Medicare doesn't cover. Medicare Advantage policies are health plans that coordinate with Part A, B and D. They are offered by most standard health carriers and replace Medigap plans.

To receive information on Medigap or Medicare Advantage plans:

Medicaid
Medicaid provides health care coverage  for low-income people and includes people who are eligible because they are aged, blind, or disabled or certain people in families with dependent children. Medicaid is a Federal program that is operated by the States, and each State decides who is eligible and the health services offered.
General information is given in the Medicaid Fact Sheet, go to: www.medicare.gov or contact your State Medicaid Program Office.