The Binder Medium is an acrylic emulsion, and its primary use is to seal a substrate prior to painting. It will give your paint a more "slippery" surface stick to, unlike a gesso which provides tooth.
If you mix it in with the Atelier Interactive paints, those mixtures will be glossier, harder and not able to be reopened when dry, acting more like a conventional acrylic.
If you mix a Traditional Medium with Atelier Interactive (Gloss, Matte, Glazing, etc), those mixtures for the most part will also be non-interactive once dry (test first!
The big differences you'll find will be in terms of sheen and in viscosity. Some will make your paint dry more level, some with brush strokes; you can feel the differences under your brush too because they are formulated differently. Make sense?