Bug type Pokémon will take double damage from Fire, Flying, and Rock-type attacks. However, they will only take half damage from Grass, Fighting, and Ground-type attacks. They will take normal damage from all other types of attacks.
Bug-type moves will do double damage to Grass, Psychic, and Dark-type Pokémon. However, they will only do half damage to Fire, Flying, Poison, Fighting, Steel, and Ghost-type Pokémon. They will damage all other Pokémon types normally.