The CVV2 (Card Verification Value 2) is a 3-digit security code that is printed on the back of your card, at the end of the signature panel. CVV2 is generally used for transactions when the card is not physically presented, such as in online purchases. It's yet another layer of protection Visa implements to help prevent fraud before it happens.
After you key in your personal and payment details during online transactions, you may be prompted for your 3-digit CVV2 Security Code. Simply check your card and enter the number. This code assures the merchant that you have your card in hand. The card issuer validates your code before your purchase can take place – giving you an extra layer of security. Used together with other verification methods, CVV2 helps protect Visa card holders from fraud when shopping online.