The order processing system begins immediately after a customer has placed their order. As mentioned, this is dependent on the payment processing service, but in the Google Checkout world the next step is authorization. During this phase, Google performs some anti-fraud checks on the customer's payment and then verifies that the payment method is good for the complete amount of the order.
If the customer's payment passes these safety checks, Google changes the payment status to Ready to Charge. This means the merchant can now log in to the Checkout service and charge the order. By default, this is a manual process for the merchant that requires logging into Google Checkout.
Once the merchant has charged the order, they must begin the fulfillment process, which includes picking the product from their shelf or warehouse, preparing it for shipping, packing, and sending. Once these steps are completed, the merchant can log in to Google Checkout and change the payment...