I am looking at the bahn.de website, for trains from Frankfurt to Berlin. Some say "Berlin Hbf", others say "Berlin Hbf (tief)" What is tief? Anything else I should know about booking trains online? Also going to Dresden.
"tief" in German is "deep". In a lot of German Hauptbahnhöfe (Frankfurt, Stuttgart, Munich), the main train tracks come in on the ground level. The tief Bahnhof is reserved for the underground S-Bahn. Berlin is upside down. Berlin is a new Bahnhof. The express train didn't come into that area, so they tunneled underground for the ICEs, etc. The S-Bahn were already above ground. So, Berlin Hbf (tief) is the underground station that serves the express (Fernverkehr) trains.