Stars are used for ranking players in the Star Cup Tiers. You are awarded 1 star for each level you win, regardless of whether you win or lose the match. There are currently 11 Tiers, starting from Rookie II and ending with Legend. All new players start from Rookie II and will then raise in Tiers as they meet the Star requirements. Once you get promoted from one Tier to the next one, you will be given a Feather reward for each of your Birds.