The elf on the shelf tradition is a holiday game that originated in the United States. It involves placing an elf figurine in different locations around the home each night, where it can observe the behavior of children. In the morning, children wake up and try to find the elf and guess where it has moved. The elf then reports back to Santa about the children's behavior and whether they have been naughty or nice. It is a fun way to keep the spirit of Christmas alive and provide a sense of magic and wonder in the holiday season.