There are two train stations at the Frankfurt airport. The Fernbahnhof (Fernbf) handles the high speed trains going completely across Germany. The Regional Bahnhof (Regbf) handles local trains and the S-Bahn going to and from Frankfurt's main station (Hauptbahnhof
) or to and from nearby stations, like Mainz or Wiesbaden.
Lufthansa and other Star Alliance airlines use Terminal 1. If you come into Terminal 2 (mostly non-Star Alliance airlines), you will have to get to Terminal 1. You can take the Skyline from the upper floor of Terminal 2 to the upper floor of Terminal 1. Or, you can take the shuttle bus from in front of Terminal 2.
To get to the Regionalbahnhof, look for stairs and escalators going down under the street just inside the outside wall of the Arrivals Hall. The Regionalbahnhof is under the building across the access road from the Terminal. The upper level of the Bahnhof has local and long distance ticket automats as well as a DB Reisezentrum.
To get to the Fernbahnhof, look for stairs or an escalator going up to the 2nd floor mezzanine. From there, you take the pedestrian bridge across the access road to the 2nd floor of the building across the street, then out through the hall, to the Fernbahnhof. The DB Reisezentrum at the Fernbf is to your left as you enter the atrium.