There were 2 main killing camps. The rest were work camps. People still got killed there but hey weren’t made specifically for that reason. the jews along with other Races and religions were forced to dig their own graves. Hitler had rooms where his soldiers would torture his victims. They would test to see how much the human body could go through without completely killing them. (Like boiling them in hot oil) They were told they were going to take showers but as soon as the water went on they would pour gas into the rooms. To get rid of the evidence they would burn the bodies (not entirely for that purpose) but when the word spread to other countries about what was really happening in the camps the Germans tried to burn everything and tried to get rid of as much evidence as possible. He main killing camp Auschwitz is almost 1/3 way burnt because of the Germans.