It is difficult to explain terrorism. Terrorism has no official criminal law definition at the international level. Common definitions of terrorism refer to the violent acts which are intended to create fear (terror). They may be done for a religious, political, or ideological goal, and uses illegal violence. Some definitions now include acts of unlawful violence and war. The use of similar tactics by criminal gangs is not usually called terrorism. The same actions may be called terrorism when done by a politically motivated group.