Other forms: eyelids
Your eyelid is the piece of skin that closes over your eyeball when you blink. The purpose of your eyelids is to protect your eye (and, of course, to be decorated with eye shadow).
When you close your eyes to go to sleep, you're actually closing your eyelids — and they are making it easier for you to sleep by blocking any light from your eyes. Humans actually have upper and lower eyelids that keep dust, sweat, and other substances out of their eyes, and also spread moisture across the entire eye with each blink.