This is a down blanket with a removal cover. Technically, the blanket itself is the “duvet,” and the cover that comes off is the “duvet cover.” It comes off so you can wash it easily (I’m assuming there are also options to swap out styles).
A “bedspread” is a heavy top cover like a duvet, but without the removable skin.
Why I Looked It Up
I had heard this word all the time, but I had no idea how it was any different than a regular bedspread.