A player must defeat eight Gym Leaders in the original Pokémon games before challenging the Pokémon League.
Each Gym Leader specializes in a particular type or battle style and awards a Gym Badge when defeated. The badges serve as proof of progress and unlock certain field abilities, such as using techniques outside battle. The eight-Gym structure became one of the defining frameworks of the main Pokémon role-playing games.
In the Kanto adventure, the Gym Leaders are Brock, Misty, Lt. Surge, Erika, Koga, Sabrina, Blaine, and Giovanni. Their locations and the order in which they can be challenged are part of the game’s progression, although some players tackle several later Gyms in a different order.
After collecting the eight badges, the player travels to the Indigo Plateau to face the Elite Four and the Pokémon League Champion. The Gym Leaders are not the same as the Elite Four, a distinction sometimes blurred in casual descriptions of the original journey.