A prison camp is a location where a group of people are incarcerated.
The survivors of the Ravinok were forced into a prison camp on Dozaria by the Breen. (DS9: "Indiscretion", "Favor the Bold")
The Romulans captured a group of Klingons at Khitomer and sent them to a prison camp in the Carraya Sector. The camp was later visited by Lieutenant Worf where he attempted to teach them about the ways of the Klingons. (TNG: "Birthright, Part I", "Birthright, Part II")