What is the difference between a matyr and a terrorist?

It is my understanding that people who take the activities of the prophet Mohamed (not sure if I spelled that correctly. My apology to Muslims if I did not) anyway...that take his lifestyle etc. as their basis for action are called fundamentalists and it is those people who use the Quran as an excuse for doing what they think will give them personal reward. A martyr (from any religion) is someone who dies because of their faith in their God. Christians have many martyrs also. A terrorist on the other hand is someone who just does what gives them satisfaction...whether it be for money, a belief or just out of plain meaness. Confusing I know. As far as killing innocents...this comes from the "killing the infidels" which as I understand it means...Not muslim people. I do not necessarily ociate Islam with terrorism. In both 911 and in Iraq, it just happens that many of those involved are fundamentalist Islam. I also believe that their are many many Muslims in Iraq and other places in the world who are just as peace loving as anyone else.