October 31 is celebrated as Halloween in the West. It was originally a Celtic custom. The Celts lived in what is now Britain, Ireland and northern France more than 2000 years ago.
Their new year began on the first of November. On the evening before, the Celts honoured the god of death. They believed the dead came to life on that evening and were allowed to visit their earthly homes.
With the emergence of Christianity, the Celtic new year became the Christian festival of All Saints Day which, at the time it was instituted (800 A.D.), was known as All Hallows Day.
The eve of this day, October 31, became known as Halloween. As the Celts used to honour their dead on this day, Halloween became associated with ghosts, witches and goblins. People were afraid to stay at home lest they be visited by evil spirits.
So they would spend the night outdoors. They sat around bonfires and told stories and ate nuts and apples.
In course of time, as superstition waned, people lost their fear of Halloween. Today it is a festival of fun. In the USA, while adults go partying, children dress up in fancy clothes and go trick-or-treating, which means if you don’t give them sweets they might play a trick on you. Many carve jack-o’-lanterns out of pumpkins. The pumpkin is hollowed out, a grotesque face is carved on one side and a lighted candle is put in. This is a carry-over of a custom from medieval times when lanterns made of hollowed-out vegetables were hung from trees and gate-posts to frighten away devils.