Or do you not know what it is yet?
The name actually explains everything. Some play for guards, others for prisoners. The prisoners want to escape by all means, even through the corpses of the guards, which is not easy, since the guards, unlike the prisoners, are armed.
Servers with a jailbreak mod usually use maps whose name starts with "jail":
CS 1.6 https://www.gs4u.net/en/cs16/search/map-jail/
CS:S https://www.gs4u.net/en/css/search/map-jail_/
CS:GO https://www.gs4u.net/en/csgo/search/map-jail_/
