art vs video art

art and video art both are nouns.

Word	Noun	Adjective	Verb	Adverb
art	Yes	No	No	No
video art	Yes	No	No	No

As nouns, video art is a hyponym of art; that is, video art is a word with a more specific, narrower meaning than art:

art: the products of human creativity; works of art collectively
video art: a type of art which relies on moving pictures and comprises video and/or audio data.

art (noun)	video art (noun)
the creation of beautiful or significant things	a type of art which relies on moving pictures and comprises video and/or audio data.
the products of human creativity; works of art collectively
a superior skill that you can learn by study and practice and observation
photographs or other visual representations in a printed publication