Auschwitz II-Birkenau and Auschwitz III-Monowitz were two different concentration camps that had different purposes and objectives.
Auschwitz II-Birkenau was the most infamous of all three Auschwitz camps. It was the one that was specifically made for killing, for performing genocide over the people that the German officials didn't thought deserve to live. This was the camp where the Jews were killed, accompanied by the Gypsies, and later by Slavic people, mostly people from the Soviet Union and Poland.
Auschwitz III-Monowitz was a camp with different purpose. The prisoners in this camp were not systematically killed, bu instead they were used as a labor force. The prisoners in this camp were overworked, they suffered from malnutrition, and had terrible conditions for living. Lot of them died because of those things, not because of direct murder. This prisoners were used as labor force for the rubber factory.
