Topics: Curtain - Wikipedia
A curtain (sometimes known as a drape , mainly in the United States) 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 vary according to cleanability, ultraviolet light deterioration, oil and dust retention, noise absorption, fire resistance, and life span. Curtains may be moved by hand, with cords, by press-button pads or remote-controlled computers. They are held out of the way of the window by means of curtain tie-backs. Measuring curtain sizes needed for each window varies greatly according to the type of curtain needed, window size, and type and weight of curtain.
Curtains are a form of window treatment, and complete the overall appearance of the house. Window treatment helps control the ambiance and flow of natural light into the room. The effect of drapery or curtains is best seen in daylight, and with proper indoor light positioning, can look attractive even at night.