A CRT (Cathode Ray Tube) is a technology used in older computer monitors and televisions. It consists of a large glass tube that contains an electron gun, phosphor-coated screen, and magnetic deflection system. When the electron beam from the gun strikes the phosphor coating, it emits light, creating the images we see on the screen. CRTs were widely used before the advent of LCD and LED displays, offering vibrant colors and high refresh rates, but they are bulky and consume more power compared to modern display technologies.