What was significant about the Battle of Normandy?

The Battle of Normandy, which began with the Anglo-American assault on the Normandy coast on June 6, 1944 (D-Day), was significant because it marked the opening of the Western front in Europe. Nazi Germany, which previously had to contend only with the Soviet Union in the East (and, to a far lesser extent, the United States in Italy) was forced to fight a two-front war. After establishing a beachhead on D-Day, the Allies drove fairly quickly through northern France, liberating Paris. After a daring and massive German counterattack was driven back in the Battle of the Bulge in late 1944 and early 1945, Germany was permanently placed on the defensive. The Normandy invasion thus marked not only a major turning point in the war, but a real death blow to Germany, which faced invading armies from the east and the west. 
https://www.history.com/topics/world-war-ii/d-day