from: http://en.wikipedia.org/wiki/Medicaid

Medicaid is the United States health program for eligible individuals and families with low incomes and resources. It is a means-tested program that is jointly funded by the states and federal government, and is managed by the states.^[1] Among the groups of people served by Medicaid are eligible low-income parents, children, seniors, and people with disabilities. Being poor, or even very poor, does not necessarily qualify an individual for Medicaid.^[2] Indeed, it is estimated that approximately 60 percent of poor Americans are not covered by Medicaid.^[3] Medicaid is the largest source of funding for medical and health-related services for people with limited income in the US.