CVV2 is an important feature ensuring security when you are using your credit card for transactions on the Internet and over the phone. "CVV" is an abbreviation for "Card Verification Value". For Discover Card the same thing is called the "Cardmember ID".
Most credit cards, such as *Visa*, *Mastercard*, and *Discover*, have a three-digit CVV2 number printed in the signature space on the back. It is always the last group of numbers in the signature space on the back of the card. Please keep in mind that it is NOT part of your regular credit card number.
The CVV2 is a means of fraud protection that helps validate two things: that the customer has the credit card in their possession and that the credit card number is legitimate.
By preventing fraud CVV2 helps keep costs down for everyone.