Is it possible to know referrals form user?

Hi.

I want to know if theres posible to know the referrals form a user, when this invite some friends sending this email invitation?..

Or how can i determine from where new users come and if they doit after receiving this invitations..

Or another thing that could be usefull is to know the number of friends has each user.. how can i know wihc is the one with more friends for example..

Is possible to know this? from admin?

Thanks!