Depending on the credit card provider in addition to your name, credit card number, expiry date and CCV number, a security code may be requested. The so-called 3-D Secure Code is a security standard for online credit card transactions and is intended to reduce the risk of fraud and the loss of payments due to card misuse. For Visa, the service is called "Verified by Visa", for MasterCard "MasterCard SecureCode" and for American Express "SafeKey".
For a payment with 3-D Secure, you will be directed to the website of your card issuer during the payment process and will confirm your identity there. Exactly how the authentication occurs depends on the card issuing institution and can be done, for example, by a password or a security question. If your card is not yet registered for the procedure, you will be automatically redirected to the required steps on your bank's website. Such codes are not stored or noted on the card itself; it is not to be confused with the CCV on the back of the credit card. Only when the authentication is successful, will the credit card payment be executed.