The RMV, oder Rhein-Main-Verkehrsbund is an organisation which brings together different types of transport in the Frankfurt and Rhein-Main areas.
Buying an RMV ticket means that you can travel to your destination using a bus, a tram, the U-Bahn or the S-Bahn – without buying a separate ticket for each system, as long as they all belong to the organisation.
RMV also offers day-tickets, weekly, monthly or even yearly tickets. The area is divided into zones. You buy your ticket based on the zones that you are travelling through.
They are just one example of many such organisations throughout Germany.
To hear a simple explanation in German, listen to the podcast:
(Press the “play” button to listen to the podcast)