Why Level Up?
Overwatch likes to reward its players with customization items each time you level up, and that’s basically the primary motivation to keep playing. You earn a Loot Box with each level you gain, and this will give you four random customization options. These can be anything, ranging from character dialogue lines and taunts, to sprays and skins for characters. You don’t have any control over what kinds of items you get, or which character you get these items for. So if you really want to get that one cool skin for Mercy, you have to keep leveling up and grabbing Loot Boxes, and hope that you get lucky.
However, there is some good news. The rewards system in Overwatch works such that you won’t ever receive duplicate items in your Loot Boxes. The duplicates will be converted to in-game credits, which you can save up to buy the skins you want for a particular hero. Even if you’re not getting four different drops as you collect more Loot Boxes, it’s still worth it for all the credits you can accumulate to spend at the store.