Even though it's quite difficult to define a common/global definition of terrorism and the main goals or motivations behind terrorist groups' plans; it has been found that regardless of the terrorist groups' ideology most of them are mainly moved by the intention of Frightening people into submission, achieving social and political changes, and destroying governments and creating anarchy.
Frightening people into submission: In order to undermine governments/states control, terrorist groups use intimidation as a strategy for getting people's submission. And that way it will be easier for them to control everything.
Achieving social and political changes:
Most terrorist groups state their main purpose is to look for ways to make changes in their societies. From their perspective, the way things are in their environment tend to be wrong, and that's why they justify their violent acts. For them, the society where they come from it's in desperate urge of help in its social or political field.
Destroying governments and creating anarchy:
From terrorist groups' perspective the government that rules their countries are inefficient or inadequate, and because of this belief, they consider the best way to fix the problem is to destroy them and create anarchy.
