A prison camp was a location where a group of people were incarcerated.
The survivors of the Ravinok were forced into a prison camp on Dozaria by the Breen. (DS9: "Indiscretion", "Favor the Bold")
In 2346, the Romulans captured a group of Klingons at Khitomer and sent them to a prison camp on Carraya IV. This camp was later visited by Lieutenant Worf when he was searching for his father Mogh. (TNG: "Birthright, Part I", "Birthright, Part II")