The Nazis called the death camps "extermination camps". There were 6 camps, Chelmno, Treblinka, Sobibor, Belzec, Majdanek-Lublin, and Auschwitz-Birkenau. Most of the people who were deported here were old, disabled, or what the Nazis considered useless. Once they got to the camps, they were immediately killed. The Nazis herded the people into big groups and used a poisonous gas to kill them. The Nazis thought that this was the most effective way to kill people. It also saved the soldiers the emotional stress that was caused by shooting people in the face.