Minecraft/Experience
Experience points (or exp. points) are orbs that glow green and yellow. Picking them up causes a green bar above your hotbar to fill up. Picking up a certain amount causes you to level up. As you reach level 9, the amount needed to level up increases with every level.
Exp. is obtained by mining ores, killing mobs and trading with villagers.
Levels are consumed when you use an anvil or an enchantment table.