A pillow cover is a removable covering for a pillow, typically made of fabric. The most common type of pillow cover is a SHAM, which is a decorative cover that is usually quilted or embroidered. A CASE is a plainer cover that is usually made of cotton or linen and is designed to protect the pillow from dirt and wear. A SLIP is a type of pillow cover that is similar to a CASE but is usually made of silk or satin and is designed to provide a luxurious feel.