show card vs poster

show card and poster both are nouns.

Word	Noun	Adjective	Verb	Adverb
show card	Yes	No	No	No
poster	Yes	No	No	No

As nouns, poster is a hypernym of show card; that is, poster is a word with a broader meaning than show card:

Other hypernyms of show card include bill, card, notice, placard, posting.

show card (noun)	poster (noun)
a poster advertising a show or play	a horse kept at an inn or post house for use by mail carriers or for rent to travelers
	a sign posted in a public place as an advertisement
	someone who pastes up bills or placards on walls or billboards