A credit card is a card which allows people to buy items without cash. Each card has a unique number. Using this number, plus other details on the card (such as the validity date, or a code), the client can buy goods or services. The issuer of the card, then transfers the money to the seller. The person using the card gets a credit. The customer has a certain amount of time to pay the credit card bill. If the bill is left unpaid for some time, the customer will have to pay interest for the amount that is left unpaid. Payment using a credit card is one of the most common methods of electronic payment.
P.S. Only have 1 to 2 credit cards to keep your credit rating up.