show card vs posting

show card and posting both are nouns.

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

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

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

show card (noun)	posting (noun)
a poster advertising a show or play	the transmission of a letter
	a sign posted in a public place as an advertisement
	(bookkeeping) a listing on the company's records