Technically, alpha software is usually fairly unstable and comes before beta.
Alpha software is generally used to find defects by the company's internal test team. When the build is stable for use it goes beta and the external beta-testers get to play with it.
Usually the final release is referred to as 'gold' or 'FCS (first customer shipment).
I know this is incredibly boring, but as a professional software test engineer it is my life... :-(
I think I will go cry myself to sleep now as I reflect on my wasted existence!