The buzz cut is the shortest hairstyle possible, while still having some hair on the head, without being actually completely shaved bald! Typically buzz cuts are where the hair is clipped / buzzed all over to just short stubbles remaining.
Short Buzz Cut (#1 / 3 mm / 1/8″ clipper guard length)
Medium Buzz Cut (#2 / 6 mm / 1/4″ clipper guard length)
Long Buzz Cut (#3 / 10 mm / 3/8″ clipper guard length)