I always think of a bedspread as a cover that goes to the floor. A coverlet is lighter weight/thinner than a comforter and both cover the mattress and box springs (never to the floor).
A lightweight down comforter I purchased from TCS was listed as a coverlet and I could easily put a duvet cover on it for change of color/pattern.

After reading CB's comment, I suppose there is a lot more confusion about this than I thought! haha. My understanding is:

1. Comforter - can be like CB described, a bed-in-a-bag thickly stuffed fluffy blanket that goes on top of the bed. It can also be a high quality down or synthetic fill fluffy blanket usually sold in white, but can come in other colors as well.

2. Duvet - is the decorative "envelope" for a plain down comforter. The comforter is placed inside the duvet and the duvet usually has one end with buttons to secure the comforter inside the duvet. This allows you to have the comfort of a down blanket with much more extravagant decorations than down comforters typically come in.

3. Bedspread - is used in lieu of a comforter most times. It is a decorative blanket, usually much thinner than a comforter and has a nice decorative detail. Is used on top of the whole bed normally. Is usually a large size that covers the length of the bed all the way down the sides to the floor

4. Coverlet - more like a quilt. Smaller than bedspread. Lots of people use these to fold at the foot of the bed and use to keep feet warm to to pull up to provide extra warmth during the night.

I think "duvet" is a confusing word; depending upon local usage and custom it can refer either to the filling or the cover.

I think "coverlet," in that the word form is a diminutive, refers to a bed covering that is either smaller or lighter (or both) than a blanket or bedspread.

THis is a big help! No wonder my coverlet doesnt fit my bed (I had previously thought it was a duvet, but didnt know what that is either)! I thought I had shrunk it in the wash. But it wasnt supposed to fit anyway. Oh well, I still like it and it's perfect for what I need it for.

Who would think bedding could be so confusing!

Here ya go...

duvet |ˌd(y)o͞oˈvā|

noun

a soft quilt filled with down, feathers, or a synthetic fiber, used instead of an upper sheet and blankets.

coverlet |ˈkəvərlət|

noun

a bedspread, typically less than floor-length.

ORIGIN Middle English: from Anglo-Norman French covrelet, from Old French covrir ‘to cover’ + lit ‘bed.’

bedspread |ˈbedˌspred|

noun

a decorative cloth used to cover a bed.

comforter |ˈkəmfərtər|

noun

1 a warm quilt.

2 a person or thing that provides consolation.

• (Comforter) the Holy Spirit.

3 dated a woolen scarf.

ORIGIN late Middle English: from Old French comforteor, from conforter ‘to comfort’

FWIW, HTH

Some hotels now don't use a bedspread (good, because they almost never washed em) and now layer woven blankets and a light coverlet, all of which are easier to wash.

A bedding catalog I use to get sold "comforter covers" and "comforter cover fillers". Rather circular!

Google is your friend :-)