What were the railroad tracks for at Auschwitz?

Answer 1

There was an extra spur built that went into the Birkenau camp, through the main gate, so that new arrivals did not need to walk so far to get to the gas chambers.

Answer 2

The railroad tracks at Auschwitz were used to transport prisoners to the camp. Trains carrying deportees from various parts of Europe would arrive at the camp, and the prisoners would be unloaded and subjected to the selection process. The tracks were a key infrastructure element in the efficient operation of the Holocaust.