The verification code is a three digit number on the back of your Visa, Mastercard or Discover card. The full credit card number is reprinted in the signature box and after the card number is the verification code.
Using the code is optional when placing an order.
Using your card verification code helps to better validate the card with our credit card processor. Basically it helps convince the processor that the customer has the credit card with them when they place an online order. Using the code helps keep our processing costs (and prices) down.