Medicare and Medicaid are both public health care programs in the United States which provide free or inexpensive subsidized health care to populations in need.
Medicare is a program aimed mainly at people over 65 and certain groups of the permanently disabled. It is a form of health insurance administered by private insurance companies but paid for by the federal government that includes coverage of prescription drugs, hospital care insurance, and general medical insurance to senior citizens.
Medicaid offers similar benefits to people under the age of 65 who meet certain criteria including lack of alternative coverage, being below a certain income threshold, or having certain types of permanent disability. It also provides coverage for children and expectant mothers living in poverty, and has increasingly provided prenatal and other forms of preventative care.
The Affordable Care Act (popularly known as "Obamacare") has expanded access and coverage for both Medicare and Medicaid.