poster vs show card

poster and show card both are nouns.

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

As nouns, show card is a hyponym of poster; that is, show card is a word with a more specific, narrower meaning than poster:

Other hyponyms of poster include show bill, theatrical poster, flash card, flashcard.

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