What is the CVV?

CVV stands for Creditcard Validation (or Verification) Value. Visa, Mastercard and American Express all have a version of the CVV to reduce merchant risk in card-not-present transactions (like internet, telephone or mail-order). The CVV code adds assurance that the consumer placing the order has access or physical possession of the credit card itself in order to use the CVV code.

Visa & MasterCard
Visa/MC CVV 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).
American Express®
AmEx CVV You can find your four-digit card verification number on the front of your American Express credit card above the credit card number on either the right or the left side of your credit card.