Cathode Ray Tube (CRT) monitors are display devices that use electron beams to create images on a phosphorescent screen. Inside the monitor, an electron gun emits beams that strike the screen's surface, which is coated with phosphor materials. When the beams hit these materials, they emit light, forming the images we see. CRTs were widely used in televisions and computer monitors before the advent of flat-screen technologies like LCD and LED. Although they provided good color reproduction and response times, CRTs are bulky and heavy, making them less popular in modern displays.