Auschwitz was initially built by Germans as a death camp for Poles but was then, from 1942, used also to extetminate Jews).

Auschwitz was originally built and largely remained a labor camp and expanded into nearby Birkenau. Auschwitz-Birkenau became a dedicadted extermination camp in 1942. The reason we know about Auschwitz is because so many laborers survived to tell the tale.

Treblinka, Belzec, Majdanek , Chelmno and Sobibor were the other dedicated extermination camps and we know, and hear much less about them, because of the extreme rarity of survivors from such places. May they rest in peace.