An affinity card is a type of credit card. The bank which issues the card gives a small amount ofmoney to a charity or institution each time the customer spends a certain amount with their card.
affinity card in British English
noun
1. British
a credit card issued by a bank or credit-card company, which donates a small percentage of the money spent using the card to a specified charity
2. US
a card entitling members of an affinity group (e.g. club, college) to a discount when used for purchases