What was the significance of the Battle of Stalingrad?

Well it did end Germany's advances into Eastern Europe and Russia. It was nazi Germany's 1st major defeat in world war 2.

The German attack on the Soviet Union in 1941 (Operation Barbarossa) after initial success, had slowed down by 1942. The Germans were trying to push forward on a front which stretched thousands of kilometres from Leningrad to Stalingrad. They also had a very precarious supply line which again stretched several thousand kilometres from Germany.

Hitler became obsessed by Stalingrad as it bore the name of his great enemy Stalin. Against the advice of his generals he split and thus weakened his forces in Army Group South with the 6th army led by Von Paulus ordered to take Stalingrad.