We land at 9:30 AM @ FRA. Frankfurt international airport.
We want to go by train to Berlin.
There are so many acronyms listed on the bahn.de website, I'm not sure what they mean. For instance, it says Frankfurt (MAIN) and Frandfurt (Main) Hbf. There are so many choices that look similar, I just don't know which to choose.
Simply, please tell me exactly what I should follow to get this train.
Thank you.

Also, how much time should we allow to get to the train after we land at 9:30 AM

You are right. It is confusing.

Frankfurt (MAIN) simply means Frankfurt am Main. Main is the name of the river which runs through Frankfurt. There is another Frankfurt in Germany.

Hbf is Hauptbahnhof, the central train station in Frankfurt. You see this for many cities in Germany where there is more than one train station.

Flughafen is the airport. Since there are more than one Flughafen stations listed you'll have to wait until another more experienced Fodorite signs on to tell you which one you need. The details of at least one Flughafen departure indicate that you take a bus and do some walking to catch your ICE to Hanover where you catch another ICE to Berlin. I thought that there is a train station in the airport.

You do not need seat reservations on these trains.

Frankfurt am Main Flughafen Fernbahnhof, is the station at FRA airport for long distance trains.

You can get a discount if you book a ticket in advance, the drawback is that these tickets are only good for a specific train, if your flight is late you'll miss your train and need to buy a new ticket. You can always purchase a full fare flexible ticket on the day of travel.

On www.bahn.de the FRA airport train station is listed as

"Frankfurt(M) Flughafen Fernbf" or just
"Frankfurt(Main)Flugh"

Both will give you the same itineraries.

I believe all trains to Berlin require a change at at Frankfurt HBF, so you could really take any local train into the city, then connect with the long distance train there.

Local (S-Bahn) trains run from the Frankfurt Flughafen Regionalbahnhof, and run every 5-10min all day long. Trip into Frankfurt takes about 10min.

Hello bizeb

We've done the same route and simply purchased our tickets at the airport rail office.

Once you land at the Frankfurt Airport, follow the signs to the downstairs rail office. These folks are extremely helpful and knowledgeable and speak English. They will get you to the right trains and stations.

This eliminates the need to pre-purchase and worry about making connections from your flight.

Happy travels!

Thank you everyone. I'm going to get the ticket at the airport.