Alpha is for 20+ patrons, 60-70% of what is planned to be added in next public release, 1 month after previous public release
beta is for 5+ patrons, 70-90% of what was planned, 2 months after previous public release
final is free, 90-100% of the content + fixes, 3 months after previous public release
all dates are not final, delays are inevitable sometimes
basically alpha and beta get early access and get to see the content earlier