To understand Islamic Terrorism, at first what is terrorism need to be clarified.
Robert Mackey, An American Political Philosopher, said about terrorism- “Terrorism is the deliberate killing of innocent people, at random, in order to spread fear through a whole population and force the hand of its political leaders.” (1) (Mackey 20 November 2009)
According to the Oxford dictionary – “The unlawful use of violence and intimidation, especially against civilians, in the pursuit of political aims.”
According to Cambridge dictionary- “Terrorism is violent action for political purposes”
Virginia Page Fortna, a philosopher has said “Terrorism is, in the broadest sense, the use of intentionally indiscriminate violence as a means to create terror among masses of people; or fear to achieve a financial, political, religious or ideological aim.” (2) (Fortna 20 May 2015)
After analyzing these definitions about terrorism, it seems that terrorism is attack against unarmed people or mass people to achieve political or religious or ideological purposes. Main reasons of attacks is to draw attention to any particular issues. So that, demands of the attackers are fulfilled.