The Potsdam Conference took place July 16-August 2, 1945 - after the war in Europe had ended with Germany's surrender. The Soviet Union, represented by Joseph Stalin, the United Kingdom, represented by Winston Churchill and Clement Atlee, and the United States, represented by Harry Truman, met in Potsdam, occupied Germany, to discuss punishment measures against Nazi German war criminals, the division of Germany and Austria between the occupying Allied nations, the adjustments of borders for German-occupied lands and Poland, and other issues. The Potsdam Declaration, issued at the same time, set forth required terms for Japan's surrender.
From Yalta, the most important outcome was that Eastern Europe was essentially awarded to the Soviet Union. This was really important because it ended up helping to start the Cold War. The West was afraid that the Soviets would expand out from Eastern Europe and that fear helped cause the Cold War.