alpha is the first release
beta is second
omega is third
and then comes final.
Alpha is basically the test release.. a select ammount of people will get to play it, they give us feedback on what they liked and what they didnt like about gameplay, level design etc etc. However, it will be reasonably un-detailed.
Beta will have taken into account what our alpha testers said and then fixed 'em.. send it to the beta testers.
Omega is final-ish. We release what we think will be all we need to do, but if anybody spots a bug, it'll get fixed.
Once completely big free, final version is released to the public.