A cathode ray tube (CRT) is a vacuum tube that uses electron beams to create images on a screen. Inside the tube, electrons are emitted from a heated filament and accelerated towards a phosphorescent screen. When the electrons strike the screen, they produce light, forming images. CRTs were widely used in older televisions and computer monitors before the advent of flat-panel displays like LCD and LED screens. Although they provided good color and contrast, CRTs are bulky and heavy, making them less practical for modern use. Today, they are mostly found in vintage electronics and specialized applications.