Alpha would be something freshly coded that has tons of bugs you need to fix before releasing it to your members. A team release would qualify as an alpha release.
Beta is usualy a first public release. It still has quite a few bugs but its not as bad as the aformentioned alpha release. Your still in the bug fixing period at this point.
Release Canidate is the final level of development one version of a script can reach. It basicly means a majority of the bugs in that particular version of the software have been fixed and the software is stable enough to be used.
As for the version control system. Its supposed to be something like this.
1.0.0
1: Major Changes - Large scale changes to the software.
0: Minor Changes - Small scale changes to the software, such as an important patch.
0: Revisions - Changing part of the software to be the same as a previous version.
Few software developers use this system anymore though. Invision Power Board for instance was recoded completly in XHTML1.0 and the version still only went up one for minor change.