Payment methods
There are several unofficially divided types of payment method implementations such as redirect payment, hosted (on-site) payment, and an embedded iframe. Two of them stand out as the most commonly used ones:
Redirect payment: During the checkout, once the customer reaches the final ORDER REVIEW step, he/she clicks on the Place Order button. Magento then redirects the customer to specific payment provider website where the customer is supposed to provide the credit card information and execute the actual payment. What's specific about this is that prior to redirection, Magento needs to create the order in the system, and it does so by assigning this new order a Pending status. Later, if the customer provides the valid credit card information on the payment provider website, the customer gets redirected back to the Magento success page. The main concept to grasp here is that the customer might just close the payment provider website and never return to your store, leaving...