CVV/CVC/CID is a 3 or 4 digit authentication number located on most credit cards to help reduce fraudulent use of credit cards for "card not present" transactions (such as Internet purchases)
Visa calls it a Card Verification Value (CVV)
MasterCard calls it a Card Verification Code (CVC)
American Express calls it a Card Identification Number (CID)
See the sample images below to locate where your CVV/CVC/CID is located
