what is a elf on the shelf

"An Elf on the Shelf is a Christmas tradition that involves a small elf doll that moves around the house and reports to Santa if children have been naughty or nice. The Elf on the Shelf is typically placed in a prominent spot in the home, such as on a fireplace mantle or on a bookshelf, and serves as a visual reminder to children of Santa's watchful eye. The elf doll can also serve as a fun addition to Christmas decorations and can be used to create a festive atmosphere in the home during the holiday season."