Difference between duvet, comforter and quilt

I want to know the difference between these three words. In Yahoo shopping, they belong to three different categories, but I regard them as the same thing. Also, please tell me the difference between bedspread, sheet and blanket. Please specially the common terms to address the piece of cloth we put on the bed as well as the one we put over our body.

a quilt is a thick embroidered blanket/comforter, usually in a checkered pattern with raised designs.

a comforter is just a thick blanket, sometimes decorated and colored, but with dye, not embroidered like a quilt.

a duvet cover covers a comforter - like a slip on decorator. Many comforters are not decorated and usually people buy one of these.

a bedspread is usually just a blanket of medium thickness that is used primarily to decorate the bed but can be sued as a functional blanket.

a sheet is a thin square piece of fabric, usually matching the fitted sheet (this goes around the bed to separate the sleeper from the mattress), that is like a blanket, but provides very little cover.

a blanket is of some thickness (not usually thin like a sheet, but it can range from close to thin to very thick) that is used for warmth. Comforter, bedspread, and quilt are all types of blankets in my opinion.

These are all my opinions on these words.