The document discusses different types and definitions of terrorism. It notes that terrorism involves acts of violence to achieve political change, but definitions depend on views of the legitimacy of causes. Terrorist groups include left-wing, right-wing, ethno-nationalist/separatist, and religious groups. While most terrorist groups achieve little, some like the PLO negotiated gains after entering politics. The document traces the history of terrorism and its evolution, including the rise of al-Qaeda and its influential 9/11 attacks, which dramatically impacted subsequent international relations events like the US "War on Terror".