An Elf on the Shelf is an elf
said to be sent by Santa, or from the North Pole, at least. They are said to watch
kids be
good during December, and report back to Santa if they're not. There are different kinds of elves, and they usually arrive between the day after Thanksgiving and the first week of December, while a
kid is between six and eleven years old. They move overnight, often give gifts, and some are very mischievous. They sometimes come with Elf Pets, (either a dog or a reindeer) which stay all year but only move with elves.