Halloween is a Celtic holiday celebrated on October 31st where people wear costumes and go door-to-door receiving candy. The holiday originated over 2,500 years ago when the Celts believed spirits walked the earth on the day the new year started. Traditionally, Celts would decorate their homes with bones and skulls to ward off spirits. Now, Halloween is widely celebrated in countries like the US and Colombia, where people hold parties in costumes and engage in traditions like trick-or-treating. Common Halloween symbols include pumpkins, black cats, owls, and vampires.