A badge is an item which denotes a Pokémon Trainer as having defeated a Gym Leader.
Trainers need to collect a certain number of Gym Badges in order to qualify for a region's Pokémon League. Young Trainers usually begin their initial Pokémon journey by traveling from city to city in order to collect all 8. Badges are small enough to fit easily between one's thumb and index finger and can be pinned to a shirt or kept in a Badge case. in order to enter the Pokémon League and challenge the Elite Four and Champion, the player must have all eight Badges from that region