flyer vs ad

flyer and ad both are nouns.

Word	Noun	Adjective	Verb	Adverb
flyer	Yes	No	No	No
ad	Yes	No	No	No

As nouns, ad is a hypernym of flyer; that is, ad is a word with a broader meaning than flyer:

flyer: an advertisement (usually printed on a page or in a leaflet) intended for wide distribution
ad: a public promotion of some product or service

Other hypernyms of flyer include advert, advertisement, advertising, advertizement, advertizing.

flyer (noun)	ad (noun)
an advertisement (usually printed on a page or in a leaflet) intended for wide distribution	a public promotion of some product or service
someone who travels by air
someone who operates an aircraft