Natures
We've all heard of natures. Some pokemon are hardy, some are jolly or maybe even something like adamant. What does this all mean? It may sound like nonsense but natures are nothing to be taken lightly. Natures have the ability to increase a pokemon's base stat by 10% or lower their base stat by 10%. So for you trainers and breeders this is something you look for. The wrong nature and your defensive wall could have 10% less its normal base defense.
Natures are not connected to Evs or Ivs in any sort. They are their own independent factor. You cannot change a nature. Once a pokemon is born with a certain nature it keeps it forever. Natures are chosen before a pokemon is born and can be passed down when breeding by giving the mother an everstone.
Natures also determine what food the pokemon enjoys and what food they will not enjoy. Natures also determine how a pokemon battles in the Battle Palace. Nature will determine if that pokemon will fight with an offensive move, a defensive move, or a support move.