web tv vs telecasting

web tv and telecasting both are nouns.

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

As nouns, telecasting is a hypernym of web tv; that is, telecasting is a word with a broader meaning than web tv:

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

Other hypernyms of web tv include television, TV, video.

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