mailer vs advert

mailer and advert both are nouns.

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

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

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

mailer (noun)	advert (noun)
a container for something to be mailed	a public promotion of some product or service
an advertisement that is sent by mail
a person who mails something

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