If you look at the front of a credit card and turn it over, you'll probably see three or four numbers slightly separated from the other numbers. These digits represent a credit or debit card's CVV, or card verification value. To better protect credit or debit cards from being tampered with, CVV's provide an extra layer of protection that helps guard against fraud, particularly for purchases made online. Most CVVs are three digits in length, but some - like American Express - have a four-digit CVV. It's found both on the back of cards as well as on the front, usually on the far middle-side right portion, just above the last five digits of the card number itself.