Common, Ledngery, and Rare Keys

Every server will have its own set of crates. These come in different types. 

Common keys give you more basic items, Ledngery keys give you more fancy items and Rare keys give you the best items

Every item in a chest has an equal chance. So if you're looking at a crate with 10 items and you want one of those items, you have a 1 in 10 chance of getting it.