Original: It was the largest of the German concentration camps , consisting of Auschwitz I ( the Stammlager or base camp ) ; Auschwitz II-Birkenau ( the Vernichtungslager or extermination camp ) ; Auschwitz III-Monowitz , also known as Buna-Monowitz ( a labor camp ) ; and 45 satellite camps .
Simplified: On 3rd September 1941 , the SS did the first testing of poison gas on prisoners at this camp .