The Card Security Code (CSC), sometimes called Card Verification Value (CVV), Card Verification Value Code (CVVC), Card Verification Code (CVC), or Verification Code (V-Code or V Code) is a security feature for credit or debit card transactions, giving increased protection against credit card fraud.
For Visa, MasterCard, and Discover Card, the code is the last 3 digits of the number printed on the back of the credit card in the signature field. For American Express, it is the 4 digit number printed on the right side above the imprinted card number on the front of the credit card.