The short answer is that you don't need to know anything about modes. Real modes are more than just scales, they are systems with rules that are used for composition. In western music, the   modal theory eventually became more cumbersome than useful, and was replaced by the major/minor system, which really includes all the modal stuff, and expands upon it--Arabic, Turkish, Persian, and Indian Classical music still use they modal systems, and they are different from ours--