Also known as the Card Verfication Code (or CVC2), it is a three-digit number imprinted on the signature panel of Visa, Mastercard, and Discover cards, and a four-digit number on the front of American Express cards to help merchants verify that the customer has a legitimate card in hand at the time of the order.
Where is the code on my card?
Visa and MasterCard cards have the three-digit value printed on the signature panel on the back of the card immediately following the card account number. The back panel of most Visa/MasterCard cards contain the full 16-digit account number, followed by the CVV2/CVC code. Some banks, though, only show the last four digits of the account number followed by the code. American Express cards have a four-digit non-embossed code located on the front of the card.