Halloween is celebrated in many countries around the world. It's most famous today as an evening when children 'trick or treat', knocking on doors in their neighborhood, dressed in costumes and hoping for treats.Halloween, or 'All Hallow's Evening' is a Western Christian yearly celebration that falls on October 31st, also known as the feast of All Saints. It's believed that it was influenced by European harvest festivals and festivals of the dead. The word Halloween was not used until the 1500s.