The term "card companies" refers to financial institutions that issue credit, debit or prepaid cards to consumers. These companies include major players such as Visa, MasterCard and American Express, among others. They operate by providing cardholders with access to a line of credit or the ability to make purchases using their own funds, while also offering rewards programs and other benefits. Card companies generate revenue through fees charged to merchants for processing transactions, as well as interest charges on outstanding balances.