Halloween originated from the ancient Celtic festival of Samhain, celebrated on October 31st. The Celts believed that on this night, the boundary between the living world and the spirit world became blurred and the spirits of the dead were able to mingle with the living. Traditional Halloween activities like carving pumpkins, dressing in costumes, and trick-or-treating evolved from Celtic traditions meant to honor the dead or appease spirits who were thought to be active on Samhain. Today, Halloween is celebrated in many countries with fall-themed activities, costumes, scary movies and more.