Cathode ray tubes (CRTs) are devices used to display images on screens, commonly found in older televisions and computer monitors. They work by firing electrons from a cathode through a vacuum tube, which then strike a phosphorescent screen, creating images. The screen is coated with materials that emit light when hit by these electrons. CRTs consist of several key components, including the electron gun, deflection system, and phosphor coating. The electron gun generates a beam of electrons, while the deflection system controls the beam's direction to create images. Although largely replaced by modern technologies like LCD and LED displays, CRTs were once the standard for visual output.