From Bulbapedia, the community-driven Pokémon encyclopedia.
Trainer classes are the types of Pokémon Trainers one can battle in all main series Pokémon games. They come in different varieties and sprites which describe their occupation, estimated age, and sometimes what Pokémon they train. For example, a Psychic is a young adult with telekinetic powers who train Template:Type2 Pokémon. All Trainer classes have overworld or field sprites that sometimes may be used for non-Trainers. Unlike in-battle sprites, overworld sprites may be shared between multiple Trainer classes such as the Ace Trainer overworld sprite, which is shared with Dragon Tamers and Pokémon Rangers. Notable Trainer classes, such as Gym Leaders, have unique sprites between each individual one. Trainer classes can be combined in certain double battles; for example a Crush Girl and a Black Belt can team up to form a Crush Kin; however, special class names are not created for Trainers involved in a Tag battle.
Beta Trainer Classes
(* Trainer class unnamed until Generation II)
(** Trainer class unnamed until Generation III)
Pokémon Battle Revolution
HeartGold and SoulSilver
Black and White