Modules are "blocks" of code that perform specific functions in the Miva Merchant admin interface. If you write a module you can have it show up almost anywhere in the admin interface so that it can be enabled and configured. For example, logging modules control the creation of log files and show up in the Logging Settings screen.
The System Extension Settings screen is kind of a catch-all for modules that don't belong anywhere else. There are three modules that show up in this screen by default, but if you install third-party modules they may also show up here.
Please see Payment > PayPal Express Checkout and/or Payments Pro for instructions on configuring this module.
Please see Payment > PayPal Payments Advanced and/or Payflow Gateway for instructions on configuring this module.
buySAFE allows your customers to add insurance to their orders during checkout