The only thing that'd ever be on top of you (because it doesnt have much of a choice-). Is usually made with a fairly soft material so you can sleep comfy, while knowing perfectly well that no one is in the bed with you because you're lonely :)
Chez: is nathan gonna be sharing your bed tonight?
Parrott: nope, just my duvet, its so sad :(
A cover, like a pillowcase, to protect and beautify a comforter, often down, because down comforters are expensive, precious, and delicate. A down comforter with a tear, rip, or hole will leak.