Hallowe’en has always been a holiday filled with mystery, magic and superstition. It began as a Celtic end-of-summer festival – Samhain, during which people felt especially close to relatives and friends who had passed. For these friendly spirits, they set places at the dinner table, left treats on doorsteps and along the side of the road and lit candles to help loved ones find their way back to the spirit world.
In the eighth century, Pope Gregory III designated November 1 as a time to honour all saints. Soon, All Saints Day incorporated some of the traditions of Samhain. The evening before was known as All Hallows Eve, and later Hallowe’en.
Today, Hallowe’en is a holiday celebrated each year on October 31 and has evolved into a day of activities like trick-or-treating, carving jack-o-lanterns, festive gatherings, donning costumes and eating treats.
Source: History.com