General question about trains in Germany

If you bought a Eurail Pass already, I guess it is too late to talk you out of wasting your money. It is not valid for trams, U-Bahns, buses. It is valid on most S-Bahn trains. You can buy local tickets or passes at most urban areas. The cheapest way is usually out of ticket vending machines located at train stations, S-Bahn stations, U-Bahn stations, and often major tram stops.

Sam,

I should have added that I work in the travel industry thus the Eurail passes were highly discounted. How do I know which of the cities on my list are S-Bahn vs U-Bahn? Is there a pass to purchase for multiple days for intercity travel for the 3 of us? We will be in Frankfurt for 2 days and Munich for 3 days.

MVV group tickets for Munich are dirt cheap. Sorry you plunked down money for a Eurail Pass...even at discounted prices you’ve overpaid significantly. You can travel all over Bavaria all day long for about 25 Euro and adding more people onto that Bavaria Pass adds only a few euro extra per person.

Frankfurt: https://www.rmv.de/c/en/start/
Munich: https://www.mvv-muenchen.de/en/index.html
Click on the ticket options.

Going to Bingen from Frankfurt is a RMV ticket, hardly worth a pass day. There are just a load of low cost ticket options in Germany. But. that is water under the bridge, or over the dam, or over the bridge.

Your trains between towns are not a problem, all covered; see also the map that comes with your pass. DB (German state railway) also operates a few InterCity (long-distance) buses that are covered and show up in train schedules. For Switzerland, see again the map to distinguish with routes are covered (solid lines) versus discounted (dashed lines).

S-Bahn means the suburban rail system which you might use from Munich to Dachau, for instance. But getting around within the city, including to BMW, you're more likely to use the U-Bahn (regular local subway system) or buses or trams, following the links that Sam gave you.

How do I know which of the cities on my list are S-Bahn vs U-Bahn?

There are no S-bahn cities and U-bahn cities. The U in U-bahn = Underground (subway system.)

The S-Bahn systems have DB (German Railways) as their parent company, which is why you can use them and not the municipal transit networks (trams, subways, buses.) The S-Bahns will only get you to certain points within Munich - as pointed out, they are essentially for suburban transport, for getting between the city and the suburbs.

Munich S-bahn: Click on the network maps to see the stops and use it all you like with your railpass...

https://en.wikipedia.org/wiki/Munich_S-Bahn

S-Bahn means the suburban rail system which you might use from Munich to Dachau, for instance.

Indeed you will find Dachau on the network maps. If you go, be aware that that's "Dachau Bahnhof" station, the rail station, but not the Dachau Concentration Camp, which requires a bus ride from the station (MVV ticket - no rail pass on the local buses.)

It's impossible to answer this question unless you tell us how many pass days you have.

Generally you won't want to waste a pass day on anything that can be covered with local/regional transit. They are at their most cost effective when you are using them for long distances on fast trains. Day trips become problematic with a Railpass - better to make a day trip an en-route trip, for example, if traveling from Berlin to Munich, stop over in Nuremberg on the way.