The elf on the shelf is a popular Christmas tradition that originated in 2005. It involves a small elf toy that is placed in a different location each day leading up to Christmas. The elf is said to be a "scout" for Santa Claus, observing children's behavior and reporting back to him on whether they have been naughty or nice. The elf typically stays in one place for a few days, then moves to a new location. It is believed that children who are kind and well-behaved will be rewarded, while those who are naughty may receive a less-than-favorable report to Santa.