The Checkout option is the most basic integration method and is easiest to implement. It allows a web merchant to call the Payments Gateway hosted payment form for entering and securely submitting transaction information. The merchant can customize the look and feel of the hosted payment form by either selecting a predefined payment form style or passing in configuration fields with the call to the payment form.
For a list of Type Definitions click here. Certain parameters are used to populate values on the payment page as read-only. Prefixing a parameter with an “e_” will allow the value to be shown as editable.
Secure Web Pay Checkout (Click Me)