how does an elf on the shelf work

An elf on the shelf is a Christmas tradition where a small elf is placed in a home to watch over the children. The elf is assigned to one family and will report back to Santa each night on the children's behavior. The elf is supposed to move around the house each day, but never let the children see him or her. This is done so that the children will think the elf is magic and be on their best behavior while the elf is watching.