Cratekeys are used for opening different kinds of lootboxes (crates) where you can win luxurious items and Silvercoins. You find these lootboxes at
By voting every day you get free keys for the VoteCrate. By opening this crate you can win ores, Silvercoins and higher quality keys selled at Minex Store.
You can buy keys for real money via Minex Store. These keys are used for opeing higher quality crates with better rewards. You can see all possible prices by hitting (left click) a crate at