Halloween is a holiday observed on October 31, the evening before All Saints Day, which is a Christian holiday. The name Halloween is derived from "All Hallows Eve," which was the evening before All Saints Day. The holiday has its roots in the ancient Celtic festival of Samhain, which marked the start of winter and was believed to be a time when the veil between the living and the spirit world was at its thinnest. People would light bonfires and wear costumes to ward off ghosts. After Christianity took hold in Europe, Pope Gregory III moved and expanded All Martyr’s Day to include saints, and had it end on November 1. The evening before All-Hallowmas was known as All-Hallows Eve and fell on the traditional ancient Celtic night of Samhain. This is the origin of Halloween.

Today, Halloween is celebrated mainly in the US and Canada, and it is a holiday for dress-up and fun, especially for children. On Halloween night, children dress up in costumes and go trick-or-treating around their neighborhood, while adults have Halloween parties. Halloween is also associated with carving pumpkins, playing pranks, and wearing scary costumes. Although Halloween has Christian roots, it is largely a secular holiday today.