Wards of the state are typically children who become the financial responsibility of the state in which they live because their parents either can't or refuse to continue to have responsibility for them. In some states, however, the phrase "ward of the state" refers to someone who is incarcerated.
Foster children are often referred as "wards of the state." Foster children, though placed in homes with people who agree to act as their guardians and who have gone through a state-conducted screening process, are not the financial responsibility of their guardians. Rather, the state agrees to cover their expenses in exchange for their guardians agreeing to supply them with a home. Foster parents are minimally compensated for their time, effort and resources. In some cases, children remain wards of the state until they turn 18. In other cases, children are wards of the state for only a short amount of time; some children are periodically wards of the state throughout their childhood.
"Ward of the state" is sometimes used interchangeably with "ward of the court." While the child is a ward of the state, all decisions regarding the child must be approved by the court. When the child is no longer under the custody of the court, or a court relinquishes custody to a guardian, the child is no longer considered a ward of the state.