History behind Halloween
Halloween started several thousand years ago with the Ancient Celts (a group of pre-Christian mystics who worshipped nature).
They considered October 31st the end of the year and they threw a big party which was known as Samhain. It was a celebration of the autumn harvest and the Celtic new year, when they believed spirits could come back and visit with living relatives.
Celts put out food and drink for the dead and left their windows, doors, and gates unlocked to give the spirits free passage into their homes. Some people believed if you left "treats" on the front porch for the spirits and ghosts, this would make them happy and they would not hurt you.
Later, as Christianity spread, November 1st became a religious holiday known as All Saints' Day. The prayer that was said on this day was called Allhallowmas. The night before became known as All Hakkiwe'en, or Halloween.