what is the story of elf on the shelf

According to legend, a special elf is sent by Santa every December to watch over children and ensure they're being good. The elf is said to have magical powers that allow him to report back to Santa each night, telling him whether the child has been naughty or nice. The elf is then given the task of helping the child be better, setting a good example, and teaching valuable lessons about kindness and empathy. If the child is good, they'll be rewarded with gifts from Santa on Christmas morning.