The IRE train is the perfect direct connection. It links regions, but does not stop at all stations.
Regional-Express (RE)
The RE train provides you with quick local connections to long-distance and S-Bahn services.
Regionalbahn (RB)
The RB train gets you to every destination. It covers regional routes and links cities to their hinterlands.
S-Bahn
In cities, S-Bahn trains are the ideal form of transport. These trains provide frequent and regular connections between cities with the surrounding area.