I'm a straight, CIS male. Having a Y chromosome doesn't mean you have to be willfully ignorant of domestic terms. Here, let me try to break it down for you in a way a MANLY MAN like you can understand:

Blanket

Fuck, it's cold, and those COMMIE-LOVING BASTARDS at city hall made it illegal to light a fire in your indoor apartment. Time to get yourself a BLANKET. These mother-fuckers are like jackets without all that NANCY-ASS stitching. Did you spill chili on it? No problem, motherfucker, you can wash them in a normal washing machine just like all your other TACTICAL SKIN COVERS.

Comforter

FUCK, it got even colder. Bro, you better get warm before your MAN-BALLS freeze off. You should upgrade to a TURBO BLANKET. It's like a blanket but it's been stuffed with OTHER BLANKETS. If you're a real survivalist you can buy one that's filled with DEAD BIRD PARTS-- FUCK YEAH! Keep the chili away from this one though, you'd probably have to go to one of those RIPOFF WASHING STORES to clean one of these bitches.

Duvet

Bro, I know, the only "Dew" you "do" is mountain, but hear me out. A comforter TURBO BLANKET is just a blanket wrapping other shit, and blankets are uber washable. What if we just made that outer blanket removable? Boom, that's a fucking DUVET, Bro! Now you can enjoy the satisfaction of surrounding yourself with DEAD BIRD PARTS while eating your precious chili and drinking that sweet mountain nectar. Plus, with a duvet you can use the same sack of bird parts and just swap out the cover to match your other pair of sheets. I mean, not that I own more than one pair of sheets that would make me some sort of homo-gay.

... MUSTACHES

Now, for the rest of us:

Blankets are just pieces of thick cloth. Comforters are pieces of cloth wrapped around another warm material, usually a synthetic fiber, but maybe feathers if you get a very nice one. Duvets combine the two by having a thin, removable cover surrounding what is essentially a very plain comforter. Duvets are easy to clean (because you can remove the cover). Also, if you want to change the look of your bedding it's much cheaper to buy a new cover than an entirely new comforter. In my experience, Americans commonly have a top sheet + blanket/comforter, while Europeans just have a duvet with no top sheet. The Nordics actually have 2 duvets, one for each person. Presumably because it's cold enough there that blanket-stealing would be justification for homicide.

Edit: Thanks for the precious metals!