An Elf on the Shelf is a Christmas tradition where a mischievous elf hides in your house to report back to Santa on the behavior of your child. It's a fun and exciting way to add some magic to the holidays. You can get an Elf on the Shelf at most major retailers or online, and they come in a variety of styles and designs. Once you've got your Elf, you can start the tradition by reading the storybook and introducing the Elf to your child. From there, the Elf will hide in a different location each day and watch over the child's behavior.