direct mail vs advertising

direct mail and advertising both are nouns.

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

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

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

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

direct mail (noun)	advertising (noun)
advertising sent directly to prospective customers via the mail	the business of drawing public attention to goods and services
	a public promotion of some product or service