You obviously don't live in England, then! It has become the most common bed cover in recent years. It is padded, normally available in winter and summer thickness, and has a loose cover put over it. It can be very snug - but since it is not tucked in, if you sleep with somebody who pulls the duvet around them, you might end up uncovered and very cold.
FYI, a duvet is not the cover (that's a duvet cover). It is either the bedding inside the cover or, colloquially, both pieces together. Some people may refer to the cover as a duvet but when you're shopping for them in a store the duvet is the inside and the duvet cover is, well, the cover. Again, some people in the U.S. might use blanket and comforter interchangeably with duvet, but they really are different things (blankets/comforters don't have covers) and each have their own words in Swedish. I am not trying to be a prescriptivist here, but if you want a duvet and ask someone to get you a comforter you will most likely not get what you actually wanted. As HaroldWonh pointed out, duvets come in different weights for different seasons. That way you just switch it out and keep the same cover. Or you can buy lots of covers to mix it up and only need the one (or two) duvets. It's way easier than having a ton of blankets and comforters + a space saver.
We used to have 'quilt' as the main translation but we've recently changed it into 'duvet' because 'quilt' is so ambiguous that it's hard to understand for many users. If you image google duvet, you will see images that look like täcke but if you image google quilt, you will see things that we call lapptäcke in Swedish.
quilt is obviously still an accepted translation.
When I was a child the “täcke” was quilted with beautiful fabrics, often red. Around 1965 my mother bought covers to our woll blankets. And a bit later you could buy quilted “täcken” that were meant to be put in a cover and had no beautiful utter layer. They were called called “istoppstäcken” because you put the “täcke” in a påslakan=cover. A “istoppstäcke” is easy to put in a washing machine, the old type of “täcke” was almost impossible to wash. “Istoppstäcke” today just is called “täcke”.
Thanks for your reply Arnauti! I see what you mean with the google search. Here in the states I believe another correct term might be comforter. Here we call a duvet the cover that goes over the comforter to protect it :) The nuances of our languages are so interesting! Thanks again!