The German word Revier literally translates as a defined area or territory. In the everyday language it does not have any relation with concentration camps, but it is used to define animal territory or a working area. The Ruhr Area is often nicknamed Revier as well.
A revier (abbreviated from German Krankenrevier, or "sick bay", "dispensary") in the language of Nazi camps was a barrack for sick concentration camp inmates. Most of the medical personnel were inmates themselves. The conditions in reviers varied drastically depending on the type of the camp.
In extermination camps (as well as in many labor camps, where extermination through labor was practiced) the idea of revier was immediately associated with death in many respects. Death was to be expected immediately upon entrance to a revier: An "insufficiently" sick person could be classified as malingerer, who is avoiding labor. The penalty was death. Even being admitted into the revier gave little hope: while the medical personnel could have highly qualified doctors (inmates), they could not offer any help beyond very basic first aid: The supply of medicine was very limited. In addition, rations for sick were lower than for the inmates who could work and no hygiene was maintained. Finally, at any moment the residents of a revier were subject to extermination for various reasons (e.g. a threat of an epidemic, due to overcrowding or deemed incurably sick).