A typical bed linen set includes a fitted sheet, a flat sheet and pillow cases. The fitted sheet is a bottom sheet and typically features elastic sides or corners, which help it fit tightly over the mattress. The flat sheet is the top sheet, which is placed over the fitted sheet and tucked in at the bottom. Pillow cases cover pillows and protect them from body oils or soiling.
Comforters, also known as duvets, are thick, soft covers that are filled with down; they are used to cover the top of the bed to provide warmth. The difference between a comforter or duvet and a quilt is that the quilt has decorative stitching--referred to as "quilting"--and is usually filled with cotton batting rather than down. A quilt fits over the bed. Quilts are also used for display on a wall. A bedspread covers the entire bed and reaches to the floor. It is used for protection and decorative purposes.
Pillow shams are decorative pillow cases and may include things like fringe and buttons. Bed skirts are decorative pieces of fabric that lay over the top of the box spring and reach the floor. Duvet covers allow homeowners to dress up an old duvet or comforter with a new look. The comforter or duvet fits inside the large pocket-like cover.