The German Empire was the German state, which contained a bunch of constituent territories. Most of these territories were the German states that had existed before unification. Prussia was by far the largest of these, and was instrumental in German unification, but a significant portion of the German Empire consisted of territories that were never part of Prussia. Prussia was historically based in North Eastern Germany (most of which is no longer part of Germany) but by the time of unification they had come to control significant territory in other parts of Germany.