Upon reaching level 1500, you will Awaken which causes your level to reset to level 1 and unlocks Prestige (https://wiki.archlightonline.com/doku.php?id=prestige&do=edit) and Feats (https://wiki.archlightonline.com/doku.php?id=feats). This also allows you to choose your specialization, which each class has 2. You can switch between the specializations freely.