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What is XP?
If you are familiar with Role Playing Games (RPGs) XP refers to experience points. XP is accrued in various ways as you interact with the game. XP is typically required to advance your character(s) to the next level. Game designers reward this behavior with new abilities and increased stats. Grinding is a term used to describe the accrual of massive ammounts of XP to increase your character's level. A player who grinds for too long will turn the game into childs play, where nothing poses a challenge, and the game design has little effect on your choices.
Now for the part where we connect RPGs to reality.