A monitor is also referred to as a VDT (video display terminal)and VDU (video display unit) , a monitor is an output device that displays video images and text.
A monitor is made up of circuitry, a screen, a power supply, buttons to adjust screen settings, and a casing that holds all of these components.
Like most early TVs, the first computer monitors were comprised of a CRT (cathode ray tube) and a fluorescent screen.
Today, all monitors are created using flat panel display technology, usually backlit with LEDs (light-emitting diode).