When you use "blanket" to refer to the cover on your bed you sleep under, what do you mean?

Posted by TDA_Liamo@reddit | AskAnAmerican | View on Reddit | 386 comments

Kind of a silly question, but I saw a meme about blankets getting twisted up at night and it made me wonder.

In the UK, I've only ever slept under a "duvet" - a fabric cover filled with insulating fibres. They come in various thicknesses, measured using tog rating, from 1 to 15 tog, where 1 is the thinnest and 15 is the thickest. If it's very hot I might get rid of the duvet and sleep under just a sheet.

I don't think I've seen this term in American media though. I see "blanket" used a lot - does this refer to a duvet, or just a thinner fabric blanket with no filling? I've also heard the term "comforter" - what does this refer to?