For the new players, once you make your character then you start going into the storyline, experiencing the scenario, and completing quests, you will not really progress in the game, you would gain experience points and level up your character first, once you've experienced the storyline, you will realise that your character is leveling up at the same time.
Rokien thread.

What doe this mean? By completing the main scenario, you'll make a significant amount of progress into a class?
S'all right I guess.