illustration vs demo

illustration and demo both are nouns.

Word	Noun	Adjective	Verb	Adverb
illustration	Yes	No	No	No
demo	Yes	No	Yes	No

As nouns, demo is a hypernym of illustration; that is, demo is a word with a broader meaning than illustration:

Other hypernyms of illustration include demonstration.

illustration (noun)	demo (noun)
a visual representation (a picture or diagram) that is used to make some subject more pleasing or easier to understand	a visual presentation showing how something works
an item of information that is typical of a class or group
artwork that helps make something clear or attractive
showing by example

illustration (verb)	demo (verb)
	give an exhibition of to an interested audience