Pokémon FireRed and LeafGreen/Natures

Natures were introduced in Pokemon Ruby and Sapphire versions. Natures boost up your stats depending on which nature your Pokemon is.

Hardy - Nothing

Lonely - Boosts attack stats

Brave - Boosts attack stats

Adamant - Boosts attack stats

Naughty - Boosts attack stats

Bold - Boosts defense stats

Docile - Nothing

Relaxed - Boosts defense stats