Trains trains and more trains

Short answer, No. Just as you would not expect to travel by air with United, Delta, Ameican and Southwest from a single website, Europe is similar. Each country has its own rail system, and there are cross border rail companies as well. But Frankfurt airport to Cologne, Cologne to Aachen, Aachen to Mainz, Mainz to Grindelwald, can all be booked at http://www.bahn.com
Grindelwald to Paris can be bought at http://www.sbb.ch/en/home.htm

German Rail, Deutsche Bahn, DB, the Bahn. They are all the same thing, the national railway company of Germany. "Eurorail", better known as Eurail is a cooperative effort of most of the European national railways to package and market rail passes. Although they show schedules online, they don't sell individual tickets. Perhaps you mean RailEurope, but they are basically a travel agency that resells tickets at a marked up price. Finally, Thalys is a consortium of French, Belgain, Dutch, and German rail that runs highspeed trains from Paris to Amsterdam through Brussels, and from Brussels to Cologne. I don't see you needing Thalys.

The webpage to find schedules all over Europe and book tickets from German Rail is http://reiseauskunft.bahn.de.

jamie,

For your trips in Germany and France, you can easily book your tickets at https://www.trainline.eu/ (you'll need to register on the site first, but that's very easy to do). In many cases you'll be able to print your tickets at home. One point to note is that if you'll be using the TGV to reach Paris, the ticket will include the compulsory seat reservations. The ticket will be specific for one train so the ticket will only be valid for the train listed on the ticket. For rail trips in Switzerland, you can use http://www.sbb.ch/en/home.html

If you haven't travelled by rail in Europe before, a couple of things to note.....

• many cities have more than one rail station, so you'll need to know the specific station you'll be using when you buy tickets.
• rail trips often involve one or more changes, so you'll have to do a bit of homework on how to do that.

If you need further information, have a look at this video - https://www.ricksteves.com/watch-read-listen/video/tv-show/european-travel-skills-part-1

This is also a helpful website from getting to different countries in Europe:
http://www.seat61.com/Europe-train-travel.htm

Jamie - you can book all but the final leg of your trip at the DB site. Here's the English-language page where you can get itineraries, ticket prices, etc.:

http://reiseauskunft.bahn.de/bin/query.exe/en

Station names in Germany:
Frankfurt(M) Flughafen Fernbf (the airport's train station for long-distance trains)
COLOGNE
Aachen Hbf
Mainz Hbf

(Hbf = main station)

Here are a couple of resources in addition to the preceding, helpful comments. 1. Access the web site "The Man in Seat 61" at http://www.seat61.com . This gives a huge amount of information about European train travel. Albeit the perspective is from a UK perspective, it mostly works the same for everyone. 2. For travel in France, I have found the website www.gare360 to be great to make it physically around the "Gares" (trains stations in France ... Like Garage in English). We've taken most of routes you've outlined, should be a fun trip.

Except Cologne is "Köln Hbf". The DB website accepts the English versions of some names, but make sure you spell the names correctly or you might get a totally different place.
The "Frankfurt(Main)" is because the full name of the city is "Frankfurt am Main", to distinguish it from "Frankfurt an der Oder" which is at the opposite end of Germany.

Jrmeier, your link to the French RR-station webpage wouldn't work for me. How about this: http://www.gares360.com/