Short answers, pulled from the story.
Terrorism, in its broadest sense, is the use of violence against non-combatants to achieve political or ideological aims. No definition has gained universal agreement, and in 2006 one estimate counted over 109 different definitions.
The word terrorism was originally used to describe the actions of the Jacobin Club during the Reign of Terror in the French Revolution. In 1795, Edmund Burke denounced the Jacobins for letting thousands of those hell-hounds called Terrorists loose on the people of France.
The Global Terrorism Database, maintained by the University of Maryland, College Park, has recorded more than 61,000 incidents of non-state terrorism. These resulted in at least 140,000 deaths between 2000 and 2014.
The Irish Republican Brotherhood, founded in 1858 as a revolutionary Irish nationalist group, has been called the first organization to use modern terrorist techniques. It began the Fenian dynamite campaign in 1881, using timed explosives to sow fear in metropolitan Britain.
The term terrorism is politically and emotionally charged, with double standards used in applying it and disagreement over the limits of the right to self-determination. Counterterrorism analyst Bruce Hoffman noted that even long-established scholars cannot reach consensus on a single definition.
The majority of terrorist attacks are carried out by military-age men, aged 16 to 40. A 2007 study by economist Alan B. Krueger found terrorists were less likely to come from impoverished backgrounds and more likely to have at least a high-school education.
In How Terrorism Ends (2009), Audrey Kurth Cronin lists six primary ways: capture or killing of a leader, entry into a legitimate political process, achievement of aims, group implosion, defeat by brute force, and transition into other forms of violence. Jones and Libicki found that of groups that ended, 43 percent converted to nonviolent political action and 40 percent were defeated by law enforcement.