Here is something that might help you understand the term, "Rakeback." This term originated online a few years ago, and it usually closely refers to how affiliates (read: partners or associates) get paid for helping poker rooms sign-up players or otherwise advertise for them. So to begin with the term "Rake."
An online poker room usually takes a small commission from each poker game just for holding it. The online poker room usually does this through the dealer who takes a small percentage of the pot from each hand, e.g., 10%-14%, and that percentage is called a "Rake." So, a "Rake" is a "Commission."
"Rakeback" is when an online poker room gives a percentage of its total "Rake" or "Commission" to the affiliates who advertise for, or otherwise promote, their business. The poker rooms normally digitally track the playing of these new players who signed up through their affiliates and then they pay back to their affiliates an agreed upon percentage based upon the rake they have gotten from these players. So, a "Rakeback" - simply stated - is a percentage of the "Rake" or "Commission."
Cardschat, for instance, may be getting a "Rakeback" from the poker rooms that they promote - and, through the digitally tracked rake that poker rooms get from the players that joined them through Cardschat, But, I do not know this for a fact.
Perhaps, I should go to Paris, and while there, I should ask the new owner of Cardschat if this is the case. But, I might not do so because the new owner of Cardschat prefers to remain anonymous for his own reasons at this time.