What does cathode ray tube mean?

A cathode ray tube is what was used in televisions and computer monitors before the advent of the LCD, LED, and Plasma tv screens. They are big, bulky, and very heavy.

They are a vacuum tube, with an approximately flat face, on the inner surface of which is deposited a phosphor. When electrons from the cathode asembly reach the phosphor, they cause it to glow at that spot.