A more thorough explanation:

The Interstate Agreement on Detainers Act is a law that was first passed in 1956. It allows a state to take custody of a prisoner who is already in another state's prison for trial. This agreement involves the federal government, certain states, and the District of Columbia.

For example, if a person is serving time in a prison in California but is wanted for a crime in Texas, Texas can request custody of the prisoner for trial. The prisoner can make a written request for disposition of the charges in Texas, and Texas must try the prisoner within 180 days of the request.

The purpose of this act is to make it easier for states to prosecute criminals who commit crimes in multiple states. It also ensures that prisoners are not held indefinitely without trial.