Hi Robbo!
A betting player is a player who is playing under a real account (not a guest) with real money.
A join is a player who has, in poker, played 500 raked hands, and in casino, deposited an agregate sum of $100 or more.
CPA is based on a join. I hope this makes sense 
If you have any further questions please do not hesitate to shoot me an email. I also have IM.
Cheers
Renee