Level and experiences
Settlers are level based game. Levels are bound to current class. Every subclass has own level.
To got next level you need to collect enough experience points. Zps are got for routine activities like killing monsters, pvp, completing questez crafting, processing, complete caravan trip.
Every new level increases amount of your base stats - health mana and energy. Levels also unlock new quests, skills, item grades, etc...
If you die, you got XP dept, this dept block your receiving of XPS, till you pays out that's debt (XP debt amount equal to XPS needed to receive first to clear that debt).
XPS are never loose.