From Bulbapedia, the community-driven Pokémon encyclopedia.
Flavor is a group of five attributes that all Berries, Pokéblocks, Poffin, and Apricorns have, in different amounts. Each flavor represents a specific Contest condition and Pokéathlon performance stat, and is liked and disliked by different Pokémon depending on their Natures. The flavor is also consistently liked or disliked depending on which stat is raised or lowered; for example, all Pokémon who like spicy flavors will have a Nature that raises their Attack, while those that dislike spicy flavors will all have a Nature that lowers their Attack. Every Pokémon will like and dislike a certain flavor unless their Nature is Hardy, Docile, Serious, Bashful, or Quirky, in which case they will have no preference.
For a list of Berries by flavor, go here.
List of flavors
As each Nature uniquely boosts one stat and hinders another; the 25 Natures may also be arranged into a table as shown:
| Nature table
|| Disliked flavor
| Favorite flavor
| No change