The document discusses the September 11, 2001 terrorist attacks on the World Trade Center in New York City and the Pentagon in Washington D.C. carried out by the terrorist group al-Qaeda. It provides background on the Twin Towers, the World Trade Center complex, and al-Qaeda leader Osama bin Laden. It describes how 19 al-Qaeda terrorists hijacked four commercial planes and crashed two into the Twin Towers, one into the Pentagon, and one into a field in Pennsylvania, resulting in 2,996 deaths.