Charges are a useful tool for additional additional amounts to a sales transaction where customers are ordering special items or you have a fixed charge that you want to apply to types of orders. These can then be charged to the customer. Examples could include a handling fee for a special time of item, some sort of surcharge for different classes of customers, setup feeds for orders. There are many different reasons why you could add a charge. Here is a quick walk through of setting up a customer charge code and used in the sales order process.
You see in this example the charges are setup as an auto charge. Charges can also be added manually to orders.