Why did the Allies invade Normandy during world war 2?

The Allies invaded Normandy to open a 2nd front against the Axis and to liberate Europe from the Germans. The invasion spot was chosen because it was weakly defended and gave great access to the interior of France.  A diversion called Operation Fortitude diverted German resources to Calais, as they believed that to be the primary landing zone for invasion, enabling the Allies to score a decisive victory.