Generation IV in the Pokémon franchise, is a term used to describe the fourth set of games and Pokémon introduced into the series. The Generation IV games introduced a number of advancements including new Pokémon, moves and gameplay features. Chronologically, these games take place in the same timeline as Generation II.
As with the other main series Pokémon games, a new set of starter Pokémon were introduced for the fourth generation. Continuing with tradition, these Pokémon are a Water-type, Grass-type or a Fire-type. They include Piplup (Water), Turtwig (Grass) and Chimchar (Fire).
Generation IV introduced a new set of Gym Leaders and the Elite Four in the Diamond, Pearl and Platinum games. All of these trainers specialize in a specific type of Pokémon and are key to progressing through the game. The HeartGold and SoulSilver Gym Leaders, Elite Four and Champion will remain the same as their predecessors.
Diamond, Pearl and Platinum (Fantina is third in Platinum)