To answer your question, WolfDragon, the day of September 11th, 2001, more known as 9/11, is the day a terrorist attack was launched on the United States. The Twin Towers were struck by two jet planes, killing over 3,000 people, including firefighters and policemen that went in and sacrificed themselves to save others. Then, the Pentagon was hit, then another plane crashed in a field in Shanksville, Pennsylvania.
Sorry for sounding so professional, I just wanted to answer your question :)