This monitor works like a television set. Color ones are made of a vacuum tube with one of its end containing three electron guns (cathodes) shooting beams (rays) of electrons at the other end which contains a screen coated with phosphor. When struck by beams, the phosphor glows. The phosphor coating each pixel is actually constructed of one red phosphor, one green phosphor, and one blue phosphor (the three basic colors). When struck by beams of different intensities, many colors are produced. In contrast to color monitors, monochrome monitors produce images of one color (often amber) against a contrasting background (often black). Monochrome monitors have one electron gun instead of three and the phosphor coating each pixel is of one color (often amber).

The phosphor does not glow for long. With time the glowing fades and the phosphor needs to be re-struck. This is done with a process called raster. With raster, the electron beams periodically re-struck every screen pixel by sweeping the screen from left to right in lines starting from top to bottom. The monitor refresh rate is the rate at which raster is performed. A monitor that refreshes the screen 80 times per second is said to have a refresh rate of 70 hertz (cycles per second). Good values are 70 to 90 hertz. Low refresh rates cause the screen to flicker.

Most CRT screens are curved, meaning that it bulges outward from its center. Some screens are curved both vertically and horizontally. Some are curved only horizontally and are flat vertically (Trinitron design). The general rule is that the flatter the screen the clearer its picture. The monitor is interfaced (connected) to the computer through a video card. For proper operation the monitor refresh rate has to be supported by the used card. Most monitors today are multiple-frequency (multisync) meaning that they support a range of refresh rates and thus can operate with different video cards.