What is the CVC code?

A Card Verification Code, or CVC, is a number that provides extra security to credit and debit card holders.  If an unauthorized person gets a hold of your account number they would not know the CVC number unless he/she actually had the card in his or her possession.

Visa, MasterCard and Discover cards have the number on the back after the your 16 digit card number.
American Express has four digits, and is located on the front of the card, on the right side.