Here are the current job classes in Ragnarok Online 2.
You start of as one of the 5 main jobs: Acolyte, Archer, Swordman, Thief or Magician.
After that each main job can, at level 20, branch out to a 2nd job. Two for each.
At level 50 you can choose between staying Neutral, Light or Dark. And your job will be for instance Dark Warrior or Light Monk and you will have new skills unlocked dependant on your choice.