Halloween is an annual festival which takes place on October 31 and has its roots in pagan customs. In ancient times, the Celtic new year, November 1, was preceded the night before by Samhain Eve. The Celts believed that on the eve of Samhain, the spirits of the dead return to earth.
Later, when Christianity began to take hold, many of the Celtic customs were adapted by Christians. In the 800's (C. E.). Pope Boniface IV established All Saint's Day by modifying the pagan celebration of the dead into a celebration of the saints and martyrs of the Catholic Church. This day was celebrated with the Allhollowmas and the night before was called All Hallow E'en.
Various customs, including the carving of jack-o'-lanterns, accompanied Halloween in the Celtic regions. Immigrants, especially those from Scotland and Ireland, brought these customs with them to the United States. Although they did not immediately catch on, Halloween celebrations were common in the U. S. by the 1800's.
In the United States, children celebrate Halloween by dressing up in a costume and going trick-or-treating. This practice involves going door to door in the neighborhood and shouting "trick or treat." Not wanting to have a trick played on them, the neighbors respond by giving the children a treat, usually candy.