Different branches and different versions. Sometimes there are regressions between new versions. Sometimes the fixes are pushed in certain branches and not others. They are generally provided for stability and compatibilities sake. If you find a version that works for your particular game. You should be able to keep it around and run your game safe and stable unless something on the game gets updated. But outside that you should probably try to run with whatever the latest stable is.

Thank you for this! I had JUST been wondering about the distinct differences. Really good timing.

Wow, straight the point. Good article!