The CVV2 Code, sometimes called CVV, CVC, or CID, is an important security feature for credit card transactions on the Internet and over the phone. "CVV" stands for "Card Verification Value."
The CVV2 number enhances fraud protection and helps to validate two things:
On a Visa or MasterCard, the 3-digit code is located on the back of your credit card, on the signature strip just to the right of the card number.
On an American Express card, the 4-digit code is on the front of the card, just above and to the right of the embossed card number.