Hello, Do you mean the movie 'Halloween' or the event? For information about the event you can see this entry in Wikipedia : https://en.wikipedia.org/wiki/Halloween Hope it helps. Have a great day.

Halloween began as the festival of Samhain. It was part of the ancient Celtic religion in Britain and other parts of Europe. At the end of summer, the Celts thought the barrier between our world and the world of ghosts and spirits got really thin. ... The Celts had a big party. Nowadays Halloween is celebrated in the US mainly through people dressing up in costumes and little children getting sweets.