screen background vs CRT screen

screen background and CRT screen both are nouns.

Word	Noun	Adjective	Verb	Adverb
screen background	Yes	No	No	No
CRT screen	Yes	No	No	No

As nouns, CRT screen is a hypernym of screen background; that is, CRT screen is a word with a broader meaning than screen background:

screen background: (computer science) the area of the screen in graphical user interfaces against which icons and windows appear
CRT screen: the display that is electronically created on the surface of the large end of a cathode-ray tube

Other hypernyms of screen background include screen.

screen background (noun)	CRT screen (noun)
(computer science) the area of the screen in graphical user interfaces against which icons and windows appear	the display that is electronically created on the surface of the large end of a cathode-ray tube