In at least some Pokemon games there are modifiers called "Natures" which affect pokemon stats. What do they do and how do it work? Also, what specific games possess it?
Natures can affect Attack, Special Attack, Defense, Special Defense, and Speed. Each nature raises one by 10% and lowers another by 10%, except for 5 "neutral natures" which leave a Pokémon's stats unchanged (or may be thought of as raising and lowering the same stat). All combinations of stats raised and lowered exist, for 20 different stat-affecting natures, and a total of 25 natures overall.
In Black and White, on the status screen's second page, on the top screen, the raised stat's name will be written in Red and the lowered stat's name will be written in Blue, though the coloration is subtle. Other games likely also have such clues.
Additionally, a nature determines what flavors a Pokémon likes the most when it comes to Berries, Poffins, Pokéblocks, and Apricorn drinks. Each flavor is tied to a stat, with a Pokémon liking its raised stat's flavor, and disliking the flavor of its lowest stat. Those with "neutral natures" have no particular likes or dislikes. The stat associations are:
Finally, a nature determines whether a Pokémon is more likely to use offensive, defensive, or supportive moves in Generation III's Battle Palace or the Battle Tent area with the same rules.