Halloween, or Hallowe'en, is a holiday celebrated on the night of October 31. Traditional activities include trick-or-treating, Halloween festivals, bonfires, costume parties, visiting "haunted houses" and viewing horror films. Halloween originated from the Pagan festival Samhain, celebrated among the Celts of Ireland and Great Britain. Irish and Scottish immigrants carried versions of the tradition to North America in the nineteenth century. Other western countries embraced the holiday in the late twentieth century. Halloween is now celebrated in several parts of the western world, most commonly in Ireland, the United States, Canada, Puerto Rico, and the United Kingdom.
The modern holiday of Halloween has its origins in the ancient Gaelic festival known as Samhain (pronounced /ˈsˠaunʲ/ from the Old Irish samain). The Festival of Samhain is a celebration of the end of the harvest season in Gaelic culture, and is regarded as 'The Celtic New Year'.
On Halloween night in present-day, adults and children dress up as creatures from the underworld (e.g., ghosts, ghouls, zombies, witches and goblins). Halloween was perceived as the night during which the division between the world of the living and the otherworld was blurred so spirits of the dead and inhabitants from the underworld were able to walk free on the earth. It was believed necessary to dress as a spirit or otherworldly creature when venturing outdoors to blend in, and this is where dressing in such a manner for Halloween comes from.
The houses are frequently adorned with pumpkins or turnips carved into scary faces; lights or candles are placed inside the carvings to provide an eerie effect.

Happy Halloween my Friend!