A credit card issuer is a financial institution, like a bank or credit union, that provides credit cards to consumers. They evaluate applicants' creditworthiness and set the terms of the card, such as interest rates and credit limits. When you use a credit card, the issuer pays the merchant on your behalf, allowing you to make purchases even if you don't have the cash on hand. Once you make a purchase, you are expected to repay the issuer, usually on a monthly basis. If you don't pay the full balance, interest charges may apply. Some well-known credit card issuers include Visa, Mastercard, and American Express.