Imagine that you’re buying something over the Internet, fax, mail or phone. Since you’re not present in person, such transactions are called “card not present transactions”. Normally, you give your card to a merchant. You take it out of your wallet, you can present your signature or prove that you know the PIN. Somehow you prove this card belongs to you. Everything goes well…
Card Security Code – usually called CVV (Visa) or CVC (MasterCard); it’s a three or four digit code located on a credit card, but not encoded on the magnetic stripe. If a client can provide such a code, it proves that he actually is in possession of the credit card and didn’t use, for example, a card number generator or a copy (skimmed) of the card.
The most common code is CVV2 (or CVC2) used in card-not-present transactions. For Visa, MasterCard, JCB, Diners Club and Discover credit and debit cards, this is a three digit code printed on the back of the card. American Express differs a bit – they have a four digit code printed above the credit card number.
Also the names of the code differ. Apart from CSC we have: