Loosely, affinity determines a character's stat boosts that are gained from supports. Supports depend on the affinities of the two characters that are being bonded, and they determine the type of bonus given. The following tables are a compilation of bonuses given by the anima affinity in each game.
The Anima affinity is considered a highly desirable affinity in the GBA games as it gives bonuses to both attack and defense, as well as Evasion. It was removed in the Tellius series, though the newly introduced Water affinity yields similar combat bonuses.