When a customer clicks on "I want a better price" button on the product details page, the popup with the custom message will be displayed. The customer has to enter his email address if he is not logged in, or just click "Send me an offer" if he is.
The Better Price extension automatically generates one-time purchase coupon code for each customer and each product based on what you've set in backend. The customer then receives an email with all the information about the discounted price and how to get it, including the unique coupon code and the expiration date of the coupon code. For configurable products the email includes the link to the product page, where customer can choose the options and add product to cart. The special discount can be claimed by entering the provided coupon code before proceeding to checkout. The Best Price Mode for this product is set to "Percent".