Samhain was one of four major Celtic seasonal festivals, along with Imbolc,
Beltane, and Lughnasadh, and it took place between the autumn equinox and
the winter solstice. 

During Samhain, the Celts harvested their crops and slaughtered livestock
for food. Then, they celebrated their abundance with sporting games and a
giant —and raucous— feast. The people also prepared winter housing for
itinerant warriors and shamans.

On a spiritual level, marked the time of the year in which the barrier
between the earthly world and the spirit world dissolved, allowing spirits
to walk among—and perhaps torment—mortals. It’s also described in countless
myths and folktales as a period of mystical intensity. Celtic priests built
huge bonfires, practiced divination rituals, and conducted rites to keep
ghouls at bay.

As part of the celebration, they wanted to light the way to their homes for
the good spirits, so they carved faces into vegetables such as turnips and
squash.