Foul Play inflicts damage. It uses the target's Attack stat to calculate damage, as opposed to the user's Attack stat. The damage calculation references the target for stat stage changes to the Attack stat but references the user for all other modifiers to Attack (including held item, Ability, and burn).
Table assumes the user is in the square marked by > facing to the right. Orange squares indicate spaces that are hit. Red squares indicate the knockback on hit Pokémon. A blue square indicates the user's position after performing the move.
Power = 47 | Accuracy = 100% | Effect = The higher the target's Attack stat, the greater the damage.