Busoshoku Haki, also known as Armament Haki, is a special ability in the One Piece universe. It allows users to create invisible armor around themselves, enhancing their physical attacks and providing protection against opponents. This ability can also be used to bypass the defenses of Devil Fruit users, making it a crucial skill in battles. To use Busoshoku Haki, a person must train their willpower and focus. It can be developed to different levels, with advanced users able to emit Haki from their bodies, allowing them to strike from a distance. This makes it a versatile and powerful technique in combat.