Answer:
They were destoyed by two hijacked planes. And it is important because the Twin Towers were the World's Trade Center in New York and were very Important to the world.
Step-by-step explanation: What happened to the Twin Towers in September 11 2001, four planes were hijacked, two of them was the cause of the destruction of the twin towers and one them destroyed half of the Pentagon. While the fourth landed in some place in Penyslavinia but still killed people.
Hope it was helpful!