Haha, this shows I should name them better :D

Version: Really "major release", so I should rename this. For GCC 4.8.1, `version` is "4.8".

Release: Really "minor release". For GCC 4.8.1, `release` is 4.8.1.

Build: Apple's build number for a given compiler. For instance, for clang, the latest build is 500. It's not really a "version" number because they track it separately but they often introduce substantive changes even if they only bump the build and not any other numbers.