📄️ Nature
Nature is a trait that each individual Pokémon has which influences how their stats grow and determines their flavor preferences. The mechanic was introduced in Generation III. A Pokémon's Nature usually affects the value of two of its stats, ultimately increasing one of its non-HP stats (Attack, Defense, Special Attack, Special Defense, or Speed) by 10% and decreasing another by 10%.
📄️ Showdown
Pokémon Showdown is an online Pokémon battle simulator. It simulates singles, doubles and triples battles in all the games out so far (Generations 1 through 9). It is a very popular environment for competitive gameplay.