A more thorough explanation:

A federal prison camp is a type of minimum-security detention facility that is operated by the federal government. These facilities are designed to house nonviolent inmates who are serving sentences shorter than a year plus one day and who are not considered escape risks. Unlike other types of prisons, federal prison camps often do not have walls or fences.

• John was convicted of a white-collar crime and was sentenced to six months in a federal prison camp.
• Mary was found guilty of tax evasion and was sent to a federal prison camp for a year.

These examples illustrate how federal prison camps are used to house nonviolent offenders who have been convicted of crimes that are not considered to be a threat to society. In both cases, the individuals were sentenced to less than a year in prison and were not considered to be a flight risk, so they were sent to a federal prison camp instead of a higher-security facility.