The term "Credit Card" was first used by a Edward Bellamy in 1887. Diners Club created the first credit card in 1950 but it required the balance be paid in full each month. In 1958 Bank of America created the BankAmericard and ushered in the modern credit card industry. In 1966 MasterCard was created by a group of banks.
Credit cards have come a long way since the 60's. Almost all adult Americans have 1 or more credit cards. The average balance carried is about $2,000. Credit cards are revolving loans in that you can pay down or draw more credit at any time so long as you do not exceed your credit limit.
There are now so many different types of credit cards that we suggest researching them on your own. Here are some good resources to start your credit card education.