Why do we celebrate Halloween?
The history of Halloween - how it all started. 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. They believed it was the time when ghosts and spirits came out to haunt, and the Celts would appease the spirits by giving them treats.