Halloween is a contraction of "All Hallows' Evening") and is also known as All Hallows' Eve.
It's a yearly celebration observed in a number of countries on October 31, the eve of the Western Christian feast of All Hallows' Day.
It initiates the triduum of Hallowmas, the time in the liturgical year dedicated to remembering the dead, including saints (hallows), martyrs, and all the faithful departed believers.
According to many scholars, All Hallows' Eve is a Christianized feast initially influenced by Celtic harvest festivals, with possible pagan roots, particularly the Gaelic Samhain. Other academics maintain that it originated independently of Samhain and has solely Christian roots.
Typical festive Halloween activities include trick-or-treating (or the related "guising" or "trunk-or-treating"), attending costume parties, decorating, carving pumpkins into jack-o'-lanterns, lighting bonfires, apple bobbing, visiting haunted attractions, playing pranks, telling scary stories, and watching horror films.
Enjoy your celebrations. But respect your neighbours, some of them just want to be left undisturbed.