A fluorescent screen converts electrical signal to visual signal, i.e., when the electron beam strikes the screen it produces a bright spot due to fluorescence.
Fluorescent screen in CRT
Cathode Ray Tube is a vacuum tube in which a fluorescent projector produces a trace of an electron beam, deflected by induced magnetic and electric fields. Cathode ray tubes have the purpose of translating an electrical signal into a visual image.
Fluorescent display in CRT
The fluorescent screen is made with phosphor. It generates light when the light strikes upon it.