Armament Haki is a special ability in the One Piece universe that allows users to create invisible armor around themselves or their weapons. This armor enhances their physical attacks and provides protection against opponents, including those with Devil Fruit powers. Users can also use Armament Haki to bypass the defenses of Logia users, who can normally turn their bodies into elements. Mastering this technique requires training and focus, making it a valuable skill for fighters like Monkey D. Luffy and Roronoa Zoro in their battles.