In an ideal world (a world where developers have the last word, not managers/marketdroids/bean counters), the tags would be:

Development Builds
something that only developers do touch... and only to develop code.

Alpha
the program is taking shape, feature list is still incomplete/being changed. Bugs abound. Final user should only toy with it to get fealing of the GENERAL direction the software is taking.

Beta
the feature list is final, there are bugs but the program is released to a wide population in order to test it and pinpoint/exterminate as many bugs as possible. Use for production work only if you like doing things over and over after crashes.

Gamma/Release Candidate
the program should be ready for release. Check everything (especially do regression testing on all bugs found). Use on production work if you like living on the bleeding edge.

Gold/Release
the copy of the program you send (used to send) to setup CD duplication.

Unfortunately, as wrote at start, tagging in the software business is marred by political/marketing issues and therfore you can expect a general shift of tags (e.g. what is labelled Beta should in fact be called Alpha).

Bye...

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