"Large maces and clubs have a wide swinging arc, and are often weighted with immense crowns. They are among the most ponderous of weapons, but successful strikes will crush enemies to powder."— Game Guide(src)
Two-Handed Maces are a larger type of maces introduced in Diablo III. Any heavy blunt weapon that uses its sheer mass is included into this class: that is their difference from Staves, which are lighter and require agility rather than strength. All classes may use Two-Handed Maces, except Demon Hunters.
Staves, Two-Handed Axes and Two-Handed Maces can all be transmogrified to each other.