It means "The more sb. goes, the more..." like in "The more you go the more your feet will hurt." Moreover this form is often used in context of *time*, in order to say "The more time passes, the more...". Then you can say 시간이 갈수록 더 예뻐질 거야. "The more time passes, the prettier she gets." / "She keeps getting prettier with time."] Other example: meogeulsurok "먹을수록..." --> "The more you eat..." (...the fatter you'll get)