direct mail vs advert

direct mail and advert both are nouns.

Word	Noun	Adjective	Verb	Adverb
direct mail	Yes	No	No	No
advert	Yes	No	Yes	No

As nouns, advert is a hypernym of direct mail; that is, advert is a word with a broader meaning than direct mail:

direct mail: advertising sent directly to prospective customers via the mail
advert: a public promotion of some product or service

Other hypernyms of direct mail include ad, advertisement, advertising, advertizement, advertizing.

direct mail (noun)	advert (noun)
advertising sent directly to prospective customers via the mail	a public promotion of some product or service

direct mail (verb)	advert (verb)
	make a more or less disguised reference to
	make reference to
	give heed (to)