The Receipt Summary control displays when the web user pays an open balance. From this control, the web user can print his/her receipt summary for his/her records and/or email this receipt to another email address. The difference between the Receipt Summary control and the Order Summary control is that the Receipt Summary control displays the receipt for payments made to an order with an open balance, where as the purpose of the Order Summary control is to let the web user know that he/she has completed the checkout process.
See Configuring the Web Settings for the Receipt Summary Control for more information.
After configuring the Receipt Summary control, your web user will see the control similar to the one displayed below.