Welcome to my small - but growing, introduction to online lingo, specificly, Online MMORGP's (see below if you don't know the acronym)! 
MMORPG - This is an acronym; it stands for: Massive multiplayer online role-playing game

RPG - Role-playing Game. 

Dupe - Duplication.  This is where are player tries to take an item (usualy in an online RPG) and illegally make duplicates.

XP - Experience points.  Gain enough, and you'll, usualy, level up.