A curtain (sometimes known as a drape)is a piece of cloth intended to block or obscure light, or drafts, or water in the case of a shower curtain. Curtains hung over a doorway are known as portieres. Curtains are often hung on the inside of a building's window to block the passage of light, for instance at night to aid sleeping, or to stop light from escaping outside the building .In this application they are also known as "draperies." Curtains come in a variety of shapes, materials, sizes, colors and patterns.