It's usually a string of numbers on the back of a credit card, the last three or four digits.
By the way, I will tell you that different credit card issuers have different security codes. If the security code is leaked, there will be money sharing. Please remember to keep your security password.
Location of different credit cards:
The security code of VISA card is called CVV2 (card verification value 2), which has 3 digits and is printed on the last 4 digits of the card number on the back of the credit card.
MarsterCard's security code is called CVC2 (Card Verification Code 2), which has 3 digits and is printed on the last 4 digits of the card number on the back of the credit card.
The security code of Discover card is called Cardmember ID, which has 3 digits and is printed on the signature column on the back of the credit card.
The security code of American Express is called CID (Card Identification Number), which has 4 digits and is printed on the front of the credit card above the credit card number.
The security code of China UnionPay is called CVN2 (card verification number 2), which has 3 digits and is printed after the 4 digits of the card number on the back of the credit card.
The security code of JCB card (Japan Credit Bureau) is called CAV2 (card authentication value 2), which has 3 digits and is printed on the back of the credit card number.
The credit card security code is equivalent to the credit card ID card, and we can use this code for consumer transactions. You don't need a password to shop on overseas websites. As long as the buyer provides the account number and security code, the transaction can be completed. In China, there are also merchants signing contracts with banks, but you don't need a credit card password, you only need a security code to complete the telephone transfer. Therefore, everyone must take good care of their credit cards, and don't let them leave their sight when spending, so as to avoid others remembering your credit card account number and security code.