The Flat Rate shipping module allows you to add a fixed cost to a customer’s order for shipping regardless of the quantity or the types of items purchased. It can be viewed as a ‘per order’ shipping cost.
If the Flat Rate Shipping Module is activated, it will appear as a shipping option during the checkout process (if the shipping option is available for the delivery address selected).
The Flat Rate Shipping Module is considered offline in that the shipping charges are calculated based on the rate entered when configuring the module. It does not rely on an external shipping processor to calculate the shipping costs in real-time during the checkout process.