November 1st traditionally marks the end of Samhain, a Gaelic festival dating back to ancient times celebrating the end of the harvest season and the preparation for Winter. Many elements of Samhain (along with All Hallows) have come down through the ages and become a part of modern Halloween traditions.
Prominent in these traditions was the building of bonfires to mark celebration and cleansing of the spirit. In addition, it was believed by those celebrating Samhain that the veil between the mortal world and the spiritual world was at its thinnest during this time period allowing interaction between humans and supernatural spirits. This belief has developed as part of Halloween emphasizing ghosts and supernatural spirits.
Samhain is still celebrated in modern times by some who practice Paganism or Wiccans. However, the celebrations can vary drastically from one group to another with some resembling the ancient holiday and others creating new traditions for celebration.
More information can be found here: https://en.wikipedia.org/wiki/Samhain