television vs web tv

television and web tv both are nouns.

Word	Noun	Adjective	Verb	Adverb
television	Yes	No	No	No
web tv	Yes	No	No	No

As nouns, web tv is a hyponym of television; that is, web tv is a word with a more specific, narrower meaning than television:

television: broadcasting visual images of stationary or moving objects
web tv: the genre of original television content produced for broadcast via the World Wide Web.

television (noun)	web tv (noun)
a telecommunication system that transmits images of objects (stationary or moving) between distant points	the genre of original television content produced for broadcast via the World Wide Web.
an electronic device that receives television signals and displays them on a screen
broadcasting visual images of stationary or moving objects