In popular Western thinking ghosts are believed to be the souls of people who have died and then appear to the living to haunt them. The Bible accepts the reality of ghosts and forbids trying to contact them (Deuteronomy 18,11). When Jesus reappeared after his death his disciples initially thought he was a ghost (Luke 24,37-39). The Pàëi word peta is often translated as `ghost' but as ghosts and petas differ significantly from each other, to do so would seem to be unjustified and confusing. A better rendering of peta would be `hungry spirit'.
According to the Buddha, beings exist as either humans, animals, gods, angry spirits, hungry spirits or purgatorial beings. Rebirth in one or another of these states depends on the kamma one has generated by one's intentional thoughts, speech and actions. The excessively greedy, constantly dissatisfied and hankering person may well be reborn as a hungry spirit. The Tipiñaka gives only brief descriptions of these spirits but in one place a leper is described as being `a peta-like human' (manussapeta, Ja.V,68), indicating that they are rather miserable beings. There is no suggestion in the Buddhist scriptures that hungry spirits can haunt humans or can be `conjured up' or contacted. However, they can, apparently, be sensitive to what their living relatives may be thinking or feeling about them.
The importance of hungry spirits in the Buddha's thinking can be judged by the fact that he considered talking about them (petakatha) to be an useless and unskillful type of speech (D.I,8). See Transference of Merit.