The domain of your main website
In general settings the domain of your main website don't seems to be important and most people will put their actual MAIN website here.
It is however a little bit problematic because the affliate program REDIRECT to this main website, that can perhaps have nothing to do with orders and the affiliate program at all.
A suggestion in this regard is a setting where admin can specify to which website/url the person clicking on the affilaite link are redireted to.
Current MAIN website is yyyy.com
Order system for separate department xxxx.com
Clicking on affiliate link get you redirected to yyyy.com where the separate department and order system is only part of our 200+ websites
SA Internet News Group cc
"I hear and I forget, I see and I remember. I do and I understand. " - Chinese Proverb