demo vs illustration

demo and illustration both are nouns.

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

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

Other hyponyms of demo include display, show, expression, manifestation, reflection, reflexion, exemplification.

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

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