The CVV2 Security Code

What is the card verification code?
The card verification code or CVV2 code is a three-digit number printed on the signiture bar of Visa, Mastercard, and Discover cards. This number is designed to help merchants verify that the customer has a legitimate card.

Where is the code on my card?
Visa and MasterCard credit/debit cards have the three-digit value printed on the signature panel on the back of the card following the credit card account number. American Express cards have a four-digit code located on the front of the card.

Visa, Mastercard, and Discover	American Express