what is the story about elf on a shelf

The story of Elf on a Shelf revolves around a magical elf sent from the North Pole to keep an eye on children during the holiday season. The elf is assigned to each family and is tasked with reporting back to Santa Claus about their behavior. The elf is invisible and only the child can see it. Each morning, the elf returns to its special spot, signaling that it has been observing the child's behavior. If the child has been good, the elf will give them a small gift or treat, but if they have been bad, the elf might get into mischief or leave a letter.