An elf on the shelf is a Christmas tradition that originated in the 1970s. It's based on the story of a magical elf who watches children's behavior throughout the year and reports back to Santa Claus. The elf is believed to have a special connection with Santa and helps him decide who has been naughty or nice. Some families place an elf in their home each Christmas season and the elf moves around the house each night, keeping an eye on the kids. It's a fun way to add a little magic and wonder to the holiday season!