The user transforms into a copy of the target right down to having the same move set.
Transform allows the user to become a copy of Pokémon. By becoming a copy of that Pokémon, the user attains their type and moves too. However, the copied moves will only have a PP of 5. In a Double Battle, the user can become copy of any Pokémon around them. In a Triple Battle, the user can only become a copy of a Pokémon that's adjacent to them.