Experience

From HammerWiki

Experience points are the primary reward for adventuring in WAR, and thus the primary means of advancement. Whenever a player kills an enemy or completes a quest, they are rewarded with experience points. Experience points represents a character becoming more experienced (and more powerful) as they achieve more in the game world. After acquiring a certain amount of experience, the character advances a rank and may gain new abilities and become stronger in his/her career.

Experience points are often abbreviated as XP or EXP.