what is elf on the shelf all about

Elf on the Shelf is a modern-day Christmas tradition in which a magical elf is placed on a shelf or other high spot in a household. The elf is said to be a scout who watches over the children and reports back to Santa if they've been good or bad. Every night, the elf flies back to the North Pole to tell Santa about the children's behavior. In the morning, the elf is magically relocated to a new spot in the house, reminding the children that Santa is always watching.