The purpose of the Order Gateway is to retrieve the next available order number from the order database so that you can reference this order to a specific customer. In SalesCart, the order gateway is only called the first time a shopper adds an item to the cart. The Order Gateway named GetOrder.php is located in the sc-bin directory and is a php script that reads the database and stores the variable.
Your customers will execute this script but will never see any actual webpage. Once the order number is retrieved, the checkout process begins.
The Order Gateway never needs to be edited!