Experience Armor is only active while you have an Experience Sword in your inventory or hotbar. Basically, just wearing it will give you experience... just for looking so cool... All the benefits of regular Emerald Armor, plus a little extra!
Gives experience just for looking so good! Also, Protection, Blast Protection, and Feather Falling.
You'll need a lot of Bottles o' Enchanting. You'll also need unused Emerald Armor. The easiest way to get the necessary bottles is to plant an Experience Tree.