Starting at level 1, you gain experience until you reach level 20. After level 20, you do [b]not[/b] level up via experience gains. Levels 21-30 are reached through equipping better gear. Rare, Legendary, and Exotic Armor pieces obtained after level 20 all contain an additional stat called Light: Light is your replacement for experience. The more Light you are given by your armor pieces, the more the yellow bar on your name plate will fill and the higher level you will become. There are two ways to increase your light level. The first is equip better armor: Legendary armor will give more light than Rare armor, and raid set and Exotic armors will give even more than that. The second is to upgrade the armor you already have: armor pieces have a set number of defense upgrades that are unlockable on their skill trees... upgrading an item's defense will also increase the amount of light it gives you while it's equipped. Right now, the maximum level one can achieve is 30, which corresponds to having a full set fully upgraded Raid Set Armor (with or without a fully upgraded Exotic piece)