CVV2 is a new authentication scheme established by credit card companies to further efforts towards reducing fraud for internet transactions. It consists of requiring a card holder to enter the CVV2 number in at transaction time to verify that the card is on hand.

Visa & MasterCard:
 

This number is printed on your MasterCard & Visa cards in the signature area of the back of the card. (It is the last 3 digits AFTER the credit card number in the signature area of the card).