mailer vs advertising

mailer and advertising both are nouns.

Word	Noun	Adjective	Verb	Adverb
mailer	Yes	No	No	No
advertising	Yes	No	No	No

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

Other hypernyms of mailer include ad, advert, advertisement, advertizement, advertizing.

mailer (noun)	advertising (noun)
a container for something to be mailed	the business of drawing public attention to goods and services
an advertisement that is sent by mail	a public promotion of some product or service
a person who mails something