Grass-type Pokémon take double damage from Fire, Ice, Poison, Flying, and Bug-type attacks. However, they only take half damage from Water, Grass, Electric, and Ground-type attacks. They take normal damage from all other attack types.
Grass-type moves deal double damage to Water, Ground, and Rock-type Pokémon. However they only deal half damage to Fire, Grass, Poison, Flying, Bug, Dragon, and Steel-type Pokémon. They deal normal damage to all other Pokémon types.