When you go to create a new character for Prophecies, you will be asked to choose a profession. Your choices are Monk, Mesmer, Elementalist, Necromancer, Ranger, or Warrior. Choosing one of these is permanent. This will be called your primary profession. In Pre-Searing you will get to choose a secondary profession, which if you complete the quest will be permanent until you leave Pre-Searing. By clicking on each class above you can learn more about each one.