Haunts, as used in this wiki, are a type of ghostly undead. They are the spirits of the dead, given form. They are humanoid in form, but do not resemble any specific person. They are bound to the mortal world by unfulfilled needs or desires, such as incomplete tasks.
Haunts differ from Ghosts in that a ghost is a recognizable person, physically resembling their former living body. They remember their mortal life.
Innistrad
In the Innistrad setting, Haunts are known as Geists.