What is the difference between Medicare and Medicaid?

Medicare is a federally funded system of health care
incorporated into the Social Security Act of 1965. It's purpose was to provide health
care for persons over age 65 who were/are legal residents of the U.S. for at least
fifteen years. It is available to persons with congenital or permanent disabilities
regardless of age. It pays 80% of all qualifying medical expenses, the remaining 20%
must be paid by private insurance or by the covered individual himself. It is funded by
a payroll tax of 2.9% of which half is paid by the employee and half by the employer,
unless one is self employed in which instance one must pay the entire 2.9%. If one has
paid the tax for not less than 40 quarters (10 years) there are no additional premiums
payable; however, if one qualifies for Medicare and has not paid the tax for 40
quarters, a premium will be assessed. There are additional provisions/qualifiers
discussed in more detail at the links noted below.

Medicaid
is a federal program to provide medical insurance for persons with limited income.
Eligibility is determined by ones means to pay, rather than ones age, as in Medicare.
Any person over 65 who meets the requirements set forth above qualifies for Medicare;
but the requirements for Medicaid are more narrowly defined. Medicaid is only partially
funded by the federal government; it is also funded by the individual states who manage
the program and the administration of its benefits. All fifty states participate in the
Medicaid program.