What is American Express Advanced Verification (AAV)?

AAV is a service set up by American Express for their card transactions. It checks the cardholder name, the telephone number, and the email address (entered by the shopper) against the equivalent records held by American Express. Useful for assessing the risk associated with a transaction, it's a standard feature at no extra cost.

To learn more about the values returned, see the Risk Management guide.
You might also be interested in Address Verification Service (AVS) and American Express Advanced Verification (AAV).