Halloween is an annual holiday celebrated on October 31. It has roots in the Celtic festival of Samhain and the Christian holy day of All Saints, but is today largely a secular celebration. Halloween activities include trick-or-treating, wearing costumes and attending costume parties, carving jack-o'-lanterns, ghost tours, bonfires, apple bobbing, visiting haunted attractions, pranks, telling scary stories, and watching horror films.
The word Halloween is first attested in the 16th century and represents a Scottish variant of the fuller All-Hallows-Eve, that is, the night before All Hallows Day. Although the phrase All Hallows is found in Old English (the feast of all saints), All-Hallows-Even is itself not attested until 1556. Thus there is no evidence of the term for this day before the 16th century Reformation.
Halloween is not celebrated in all countries and regions of the world, and among those that do the traditions and importance of the celebration vary significantly. Celebration in the United States has had a significant impact on how the holiday is observed in other nations. This larger American influence, particularly in iconic and commercial elements, has extended to places such as South America, Europe, to Japan under the auspices of the Japanese Biscuit Association, and other parts of East Asia. (From: Wikipedia, license: CCA-SA)