The group developed ideas—such as targeted killing of the leaders of oppression—that were to become the hallmark of subsequent violence by small non-state groups, and they were convinced that the developing technologies of the age—such as the invention of dynamite, which they were the first anarchist group to make widespread use of—enabled them to strike directly and with discrimination.David Rapoport refers to four major waves of global terrorism: "the Anarchist, the Anti-Colonial, the New Left, and the Religious. The first three have been completed and lasted around 40 years; the fourth is now in its third decade." Infographics
Types
Depending on the country, the political system, and the time in history, the types of terrorism are varying. In early 1975, the Law Enforcement Assistant Administration in the United States formed the National Advisory Committee on Criminal Justice Standards and Goals. One of the five volumes that the committee wrote was titled Disorders and Terrorism, produced by the Task Force on Disorders and Terrorism under the direction of H. H. A. Cooper, Director of the Task Force staff. The Task Force defines terrorism as "a tactic or technique by means of which a violent act or the threat thereof is used for the prime purpose of creating overwhelming fear for coercive purposes". It classified disorders and terrorism into six categories:
Civil disorder – A form of collective violence interfering with the peace, security, and normal functioning of the community.
Personal and social factors
Various personal and social factors may influence the personal choice of whether to join a terrorist group or attempt an act of terror, including:

Identity, including affiliation with a particular culture, ethnicity, or religion
Previous exposure to violence
Financial reward (for example, the Palestinian Authority Martyrs Fund)
Mental health disorder
Social isolation
Perception that the cause responds to a profound injustice or indignityA report conducted by Paul Gill, John Horgan and Paige Deckert found that for "lone wolf" terrorists:
43% were motivated by religious beliefs
32% had pre-existing mental health disorders, while many more are found to have mental health problems upon arrest
At least 37% lived alone at the time of their event planning and/or execution, a further 26% lived with others, and no data were available for the remaining cases
40% were unemployed at the time of their arrest or terrorist event
19% subjectively experienced being disrespected by others
14% percent experienced being the victim of verbal or physical assaultAriel Merari, a psychologist who has studied the psychological profiles of suicide terrorists since 1983 through media reports that contained biographical details, interviews with the suicides families, and interviews with jailed would-be suicide attackers, concluded that they were unlikely to be psychologically abnormal. In comparison to economic theories of criminal behaviour, Scott Atran found that suicide terrorists exhibit none of the socially dysfunctional attributes—such as fatherless, friendless, jobless situations—or suicidal symptoms. By which he means, they do not kill themselves simply out of hopelessness or a sense of having nothing to lose.Abrahm suggests that terrorist organizations do not select terrorism for its political effectiveness.