charge card vs open-end credit

charge card and open-end credit both are nouns.

Word	Noun	Adjective	Verb	Adverb
charge card	Yes	No	No	No
open-end credit	Yes	No	No	No

As nouns, open-end credit is a hypernym of charge card; that is, open-end credit is a word with a broader meaning than charge card:

charge card: a card (usually plastic) that assures a seller that the person using it has sufficient means of payment and that the issuer will see to it that the seller receives payment for the merchandise delivered
open-end credit: a consumer credit line that can be used up to a certain limit or paid down at any time

Other hypernyms of charge card include positive identification, charge account credit, revolving credit.

charge card (noun)	open-end credit (noun)
a card (usually plastic) that assures a seller that the person using it has sufficient means of payment and that the issuer will see to it that the seller receives payment for the merchandise delivered	a consumer credit line that can be used up to a certain limit or paid down at any time