In the billing, there is Program description button. Click and read what is written over there.
P.S. You can see full details of your clients if you use Reseller program.
Reseller is mainly a person who installs eaquipment to his clients, he must understand sharing and install the equipment to those who does not understands the issue. За них продляет подписки и т.п.
Referal can be any person, even the person who does not use sharing and does not know what is it. He attracts people with his link (referal link) and gets % from their purchases.