The main reason Germany invaded the Soviet Union was in order to obtain access to their oil supply. The reason for choosing Stalingrad was due to the fact the it had the name of Adolf Hitlers sworn enemy 'Joseph Stalin' in the name.
So who own the battle? The German's surrendered to the Russians by mid-January due to the fact that their soldiers could not survive the winter in Russia.
The significance is that the Russians were able to defeat Adolf Hitler and his Military largely due to the fact that the Germans got caught in bad conditions.