Halloween is a pagan festival celebrated on October 31st, the eve of All Saints Day. It originated as a Celtic festival called Samhain, marking the end of the harvest season. Modern Halloween traditions involve children dressing up in costumes and going door-to-door saying "trick or treat," receiving candy. Adults also celebrate through costume parties. While Halloween has traditional pagan roots and focuses on fun, All Saints Day is a Catholic religious observance commemorating deceased saints.