Munich to Vienna on Railjet-- Question #2

George, "über" is German for via (with a ü, not a u, these are two different letters in German).
So all it is saying is that your ticket is valid *via Rosenheim * Traunsterin * Freilassing * Salzburg Stadt *, and on the way back via Linz * Salzburg Freilassing * Traunstein * Rosenheim.
These will be places (rail junctions) your train goes through. They are not necessarily where it stops, but the route is used to calculate the fare. I looked up times for a random train (actually RJ60) and the stops are:

Wien Hbf 10:21
Wien Meidling 10:35
St.Pölten Hbf 10:58
Linz Hbf 11:46
Salzburg Hbf 12:52
München Hbf 14:30

UBER Rosenheim * Traunsterin * Freilassing * Salzburg Stadt
And the Vienna to Munich ticket says:
UBER Linz * Salzburg Freilassing * Traunstein * Rosenheim
What does this all mean?

It simply describes the route you have booked and prevents you from making a big detour on that ticket through, say, Graz and Klagenfurt to Salzburg.

Thank you for your answer.

The list of towns lists the stops the train will make in that order, über is "via"

Most RailJets don't make any stops between Salzburg and Munich, but the route via Rosenheim, Prien, Traunstein, and Freilassing is the only route they take..