Curtain is a piece of cloth intended to block or obscure light, or drafts, or water in the case of a shower curtain. A curtain is also the movable screen or drape in a theater that separates the stage from the auditorium or that serves as a backdrop. Curtains hung over a doorway are known as portières. Curtains are often hung on the inside of a building’s windows to block the passage of light, for instance at night to aid sleeping, or to stop light from escaping outside the building (stopping people outside from being able to see inside, often for privacy reasons). In this application, they are also known as “draperies”. Curtains come in a variety of shapes, materials, sizes, colors and patterns, and they often have their own sections within department stores, while some shops are completely dedicated to selling curtains.