What is "rhein-express"

The Rhein-Express is a Regional-Express (RE 5) service, which generally follows the Rhine river. It runs daily every hour from 5 am to 9 pm from Emmerich via Wesel, Oberhausen, Duisburg, Düsseldorf, Cologne, Bonn, Remagen and Andernach to Koblenz, in the German states of North Rhine-Westphalia and Rhineland-Palatinate.