Halloween is a holiday combining ideas of traditional harvest celebrations with more modern and social customs such as costume wearing, trick-or-treating, and spooky decorations based on the changing of the seasons, death, and the supernatural (like ghosts).
It is common to trace its roots back in time to a pagan festival of ancient Ireland known as Samhain (pronounced sow'-en or sow'-een). The prehistoric (meaning before history was written down) observance is said to have marked the end of summer and the start of winter. It was celebrated with feasting, bonfires, sacrificial offerings, and remembering people who had died. There was a belief that this was the time of year when the physical and supernatural worlds were closest and magical things could happen.