Why did nazi germany build concentration camps in poland

The Nazi Germany built concentration camps all along the German-occupied territories in order to make war prisoners work while living in extreme poor conditions. Thousands of ordinary people were imprisoned and enslaved as a condition to respond to the German war effort. Prisoners who suffered from starvation, diseases and executions had been put into these camps because of the racist policies.

During the Holocaust the Germans turned Auschwitz into the major concentration death camp  because of its extermination facilities. Besides, a great number of Jews lived in Eastern Europe, particularly in Poland. Jews   were taken to Auschwitz death camp, killed by annihilating gas in the chambers and then, their bodies were burnt in the crematoria. At this place, the Germans could hide the evidence of these crimes.