Bedding items are essential components of a comfortable and inviting bedroom. A SHEET is a flat rectangular piece of fabric used to cover the mattress, usually made of cotton or linen. A DUVET is a large, thick quilt filled with down or synthetic fibers, often used as a blanket in colder climates. A SHAM is a decorative pillowcase, usually made of fabric with an ornamental design. All three items are necessary for a complete bedding set.