masking vs hiding

masking and hiding both are nouns.

Word	Noun	Adjective	Verb	Adverb
masking	Yes	No	No	No
hiding	Yes	No	No	No

As nouns, hiding is a hypernym of masking; that is, hiding is a word with a broader meaning than masking:

masking: the act of concealing the existence of something by obstructing the view of it
hiding: the activity of keeping something secret

Other hypernyms of masking include concealing, concealment.

masking (noun)	hiding (noun)
the act of concealing the existence of something by obstructing the view of it	the activity of keeping something secret
scenery used to block the audience's view of parts of the stage that should not be seen	the state of being hidden
the blocking of one sensation resulting from the presence of another sensation