Experience is accumulated by defeating monsters as well as by consuming EXP cards, which are awarded when completing certain quests. There are two types of experience:
- EXP: character experience, used to improve your level.
- CLS: class experience, used to rank up, allowing you to improve and unlock classes.
You can check both experience gauges below your quick slot bar. Monsters give both types of experience, at a varying rate. Note that your companion also gains EXP.
You can consult the experience tables on TOSBase.