Wiktionary
experience points
n. (context gaming English) A set of points when a predetermined amount is accumulated by a player character, causes them to level up. This is one of the core mechanics of many role-playing games. Abbreviations: EXP or XP.
Usage examples of "experience points".
They paid ten ceramics apiece for the privilege of creating new characters and remaining in the game, though they lost not only their previous wagers, but all of their experience points as well, since their characters had died.
Inform the possessor that, by using this sword, he will gain more experience points.
See, the more experience points your character earns, the more power he gets.