A monitor or a display is an electronic visual display for computers. The monitor comprises the display device, circuitry and an enclosure. The display device in modern monitors is typically a thin film transistor liquid crystal display (TFT-LCD) thin panel, while older monitors use a cathode ray tube (CRT) about as deep as the screen size.
A monitor is a device that is used to check or display the progress of something. It is also used for data processing and enhancing of graphics capabilities. Read more about it at http://www.webopedia.com/TERM/M/monitor.html.