The elf on the shelf is a tradition that began in Germany in the 1800s. The tradition involves a small elf figurine that is placed on a shelf or in another high place by parents, and the elf watches over the children to see if they've been good or bad. The elf moves from place to place during the night, reporting back to Santa if the children have been good or bad. The tradition has become a beloved part of Christmas culture, and many families still participate in it.