Although a clear cut definition of terrorism is difficult to formulate, several basic elements distinguish it from other forms of violence.

Terrorism differs from other forms of military action in that noncombatants are deliberately targeted. In a conventional war, revolution or guerilla action, the fighting usually takes place between military or paramilitary groups. So called "legitimate" targets typically include soldiers, insurgents and civilian leaders of the warring parties. In any conflict noncombatants are often caught in the crossfire, but they generally are not specifically targeted. Modern militaries make a particualr effort to avoid unnecessary civilian casualties, referred to as collateral damage in military-speak.

Terrorists on the other hand, focus their efforts on noncombatants. That is not to say terrorists will not attack government or military targets, but for their purposes, attacking civilians yields better results. While revolutionaries and guerillas seek military victory against their government, terrorist movements attempt to affect change through political pressure.

For revolutionary movements to form, there needs to be widespread discontent with a government or its policies. Consequently, those movements tend to be majority movements, or at least have a wide base of support. On the other hand, terrorist groups are usually rather small with a very limited support base. So with their limited resources, terrorists cannot pose a credible military threat to the government. Instead they attempt to create a climate of fear and instability in society by committing indiscriminate acts of violence. Terrorists hope their tactics will lead to public outcry for the government to cede to whatever demands the terrorists may pose in order to stop the violence.

Terrorists are often labeled common criminals and treated as such. Although terrorists acts are criminal acts, their activities and motivations are much more complicated. When an individual robs a bank, store, person, etc., he or she is seeking money, or more generically, an increase in wealth. If a person murders another the motive is usually financial gain or some personal matter.

When terrorists commit acts of robbery, murder, extortion or kidnapping for ransom, they are usually seeking funding for their activities (weapons, equipment or recruitment) or media attention for their particular cause. Of course, many terrorits will probably not shy away from monetary gain, but that is not the primary goal.

In summary, the difference between terrorism and crime is motive. In committing crime, a "common criminal's" end goal is an increase in wealth or settlement of a personal score, while a terrorist's end goal is political, ideological or social change. For a terrorist, the commission of crime is a necessary evil in achieving that end goal.

Although a multitude of terrorist groups with a wide variety of goals exist, nearly all of them can be classified into four basic categories outlined by British terrorism expert Paul Wilkinson.

The above discussion concerned individual level terrorism, where individuals or groups terrorize a society or government in order to achieve a desired change. State terrorism on the other hand, refers to a government committing acts of violence against its own citizens.

Joseph Stalin's purges in the U.S.S.R., where thousands were executed or imprisoned for apparent anti-communist activities and sentiments, are good examples. More recent examples include the "dirty wars" of the 1980's in Latin American nations like Argentina, Guatemala and El Salvador. The authoritarian governments of these nations created clandestine death squads to eliminate members of opposition groups and anyone else who expressed dissent, including members of the clergy.

Debate over whether so called state terrorism fits the definition of terrorism continues. State terrorism does not manifest itself in random acts of violence, instead individuals are targeted because of activities they are involved in or views they have expressed. State terrorism is not indiscriminate violence, since people generally know what types of activities can elicit reprisals from the government. Nonetheless, government sanctioned violence against citizens to eliminate dissent does fit both FBI and Department of Defense definitions of terrorism.

The United States government maintains a list of nations which it considers to be sponsors of international terrorism. Nations that support, tolerate or engage in international terrorism are considered state-sponsors of terrorism.
Seven nations are currently listed as supporting terrorism by funding, training, supplying or providing safehaven to known terrorists. Cuba, Iran, Iraq, Libya, North Korea, Sudan and Syria currently hold this distinction.

Iran is the most notorious and active sponsor of terrorism, utilizing its own agents and a variety of Islamic terrorist groups it supports and sometimes directs. Iran has been accused of assassinating dissidents abroad and funneling money, weapons and intelligence to Middle Eastern terrorist groups like Hizballah, Hamas and the Popular Front for the Liberation of Palestine - General Command (PFLP-GC). These groups have committed numerous attacks against American and Israeli targets.

The U.S. and its allies consider the actions of these nations serious impediments to counterterrorist efforts and international security. Therefore, sanctions are often imposed on terrorist-sponsoring nations in order to compel them to discontinue support.

(Information taken from the 1995 Patterns of Global Terrorism)