postal card vs postcard

postal card and postcard both are nouns.

Word	Noun	Adjective	Verb	Adverb
postal card	Yes	No	No	No
postcard	Yes	No	No	No

As nouns, postal card and postcard are synonyms defined as:

postal card and postcard: a card for sending messages by post without an envelope

Other synonyms of postal card include mailing-card, post card.

postal card (noun)	postcard (noun)
a card for sending messages by post without an envelope	a card for sending messages by post without an envelope