What Is a CRT, and Why Don’t We Use Them Anymore? What Is a CRT? In the context of electronics, CRT stands for “cathode ray tube.” It’s a technical term for the glass picture tube inside of a vintage TV set or computer monitor—the kind used before flat-screen displays became common. CRTs are electronic image display devices that have the advantage of showing information dynamically without the need for moving parts. When someone says “a CRT,” they might also be referring to a TV set or monitor that uses a CRT instead of the actual cathode ray tube itself.