This lets you switch the operation of the payment system as follows:

• ON – the payment system is active and is available for customers to select for payment
• OFF – the payment system is disabled
• TEST – the payment system is set in test mode; it will only be visible at checkout if you are logged in as a store admin. Orders will be passed with a 'test' flag so cards will not be billed.
• FAKE – an additional test setting; this simulates an order callback without sending anything to the payment gateway. It is a useful way to test the settings and see what happens with successful orders but without having to repeatedly go through the payment stage on the remote site.