Undead are beings that exist in the world past the dead of their corporeal body, in forms that are no longer truly alive. This broad classification consists of a variety of types of creatures that could loosely be considered races.
Other undead persist in the world despite having no tangible form. Their ability to interact with the physical world is limited without the use of telekinesis or other forms of magic. Examples of incorporeal undead include ghosts and wraiths.