Extermination camp (German: Vernichtungslager) and death camp (Todeslager) are usually interchangeable and specifically refer to camps whose primary function is or was genocide.
In a generic sense, a death camp was a concentration camp that was established for the purpose of killing prisoners delivered there. All ages of people were killed at these camps. They were not intended as sites for punishing criminal actions; rather, they were intended to facilitate genocide. Historically, the most infamous death camps were the extermination camps built by Nazi Germany in occupied Poland during World War II.
Nazi-German extermination camps are different than concentration camps such as Dachau and Belsen, which were mostly intended as places of incarceration and forced labor for a variety of “enemies of the state”—the Nazi label for people they deemed undesirable. In the early years of the Holocaust, the Jews were primarily sent to concentration camps, but from 1942 onward they were mostly deported to the extermination camps.
Extermination camps should also be distinguished from forced labor camps (Arbeitslager), which were set up in all German-occupied countries to exploit the labor of prisoners of various kinds, including prisoners of war. Many Jews were worked to death in these camps, but eventually the Jewish labor force, no matter how useful to the German war effort, was destined for extermination. In most Nazi camps (with the exception of POW camps for the non-Soviet soldiers and certain labor camps), there were usually very high death rates as a result of executions, starvation, disease, exhaustion, and extreme brutality; nevertheless, only the extermination camps were intended specifically for mass killing.
The distinction between extermination camps and concentration camps was recognized by Germans themselves (although not expressed in the official nomenclature of the camps.). As early as September 1942, an SS doctor witnessed a gassing and wrote in his diary: “They don’t call Auschwitz the camp of annihilation (das Lager der Vernichtung) for nothing!” When one of Adolf Eichmann’s deputies, Dieter Wisliceny, was interrogated at Nuremberg, he was asked for the names of extermination camps; his answer referred to Auschwitz and Majdanek as such. When asked “How do you classify the camps Mauthausen, Dachau and Buchenwald?” he replied, “They were normal concentration camps from the point of view of the department of Eichmann.”