The Card Verification Value (CVV/CVV2) or Card Verification Code (CVC) is a security feature that helps verify that the person entering payment information is in possession of the actual card.
For most debit and credit cards, this is a three-digit number found on the signature panel on the backside of the card.
If you're using an American Express (AMEX) card, the CVV, often referred to as the CID (Card Identification Number), is a four-digit number located on the front of the card, just above and to the right of the card number.