The CVV (Card Verification Value), also known as the CVV2 for Visa, CVC2 for MasterCard, and CID for American Express, is a three- or four-digit number on your credit or debit card. This number is an additional security feature that helps to verify that the cardholder is in possession of the card during non-physical transactions, such as online purchases or over-the-phone payments. The purpose of the CVV is to ensure that the person making the transaction has the card in their possession and that the card number hasn't been stolen or used fraudulently.