The user's attacks do 25% more damage to Pokémon as the same gender as the user; the user's attacks do 25% less damage to Pokémon of the opposite gender as the user. If either Pokémon has no gender, there is no change in damage.
The user's attacks ignore any of the target's abilities that could prevent their damage or effect. This includes Levitate, Soundproof, Water Absorb, Motor Drive, etc.; this includes abilities that prevent effects or conditions, such as Clear Body, Shell Armor, Sticky Hold, etc.; abilities that lower damage or accuracy, such as Simple, Sand Veil, Thick Fat, etc.; and abilities that prevent the user from hitting its target, such as Lightningrod and Storm Drain.