Ghosts are alleged to be disembodied spirits or souls that sometimes, at least in popular accounts or myth, appear as silvery or shadowy apparitions, or sometimes invisibly (these are alleged to make noises and/or telekinetically displace objects are known as poltergeists). Beliefs about ghosts have varied over time and place, with disagreement both as to what ghosts are (supposed to be) and whether such a thing exists. Recent studies indicates that many Westerners believe in ghosts and an afterlife, and belief in an afterlife is an essential part of Islam and Hinduism.
In the West, those who believe in ghosts sometimes hold them to be souls that could not find rest after death, and so linger on Earth. The inability to find rest is often explained by lingering, unfinished business, such as a victim seeking justice or revenge after death, or a criminal lingering to avoid Purgatory or Hell. It is sometimes held that ghosts reside in Limbo, a place, according to some Catholic doctrine, between Heaven and Hell where the souls of unbaptized infants go.
In the East (such as China), people believe in reincarnation. Ghosts are those souls that refused to be 'recycled' because they have unfinished business similar to those in western belief. Exocists can either help a ghost to be reincarnated or blow it out of existence. In Chinese belief, besides reincarnation, a ghost can also become immortal and become demigod, or it can go to hell and suffer till eternality.
In most cultures, the appearance of ghosts are associated with a chilling sensation. Some believers claim ghosts are related to some kind of negative energy. But a natural animal response to fear is hair-raising which can be mistaken as chill. Ghosts are also associated with seeking justice or revenge almost in all culture. It serves as an effective scare tactic against killers in all society.