there were 3 parts of the battle. There was the attack, the first wave, and the second wave.
In the attack, the Allies needed to invade when there was a full moon for light, so they only had a small duration to invade. General Eisenhower agreed to attack, despite overcast skies. The weather affected the Allies ability to attack, but it made the germans more surprised and unprepared. The Allies attacked during high tide to avoid obstacles germans had put in the water.
in the first wave, it all started with paratroopers, or men who jumped out of planes using parachutes. They usually jumped at night and landed behind enemy lines. Their job was to destroy key targets and capture bridges in order for the main invasion force to land on the beaches of Normandy, France. Thousands of dummy soldiers were dropped in order to draw fire and confuse the enemy.