Otherwise known as Poltergeists, ghosts are often a tragic, although there can be beneficial, negative or neutral ghosts- the spirits of dead people. Ghosts are often believed to haunt a location or someone living, sometimes appearing as a warning.
A lot of western ghosts populate "ghost towns" which are once-thriving cmmunities that have been abandoned by humans.
A lot of ghosts are purely there because of roots such as dying in that location, or attatching to a person.
Some love to cause mischief and fear by scaring the inhabitants of the building in ways such as knocking objects over and creating noises.