I rarely listen to tunes in my '09 Sport but I do on occasion.

But in the center of the volume button, it says "Push" and the only thing I see is that "RDS" appears on the left side of the display with no other changes. What does this actually do?

 

I think that's what shows when there's not radio station information to display. Like the station call numbers.

 

There is a button (not the one I'm referring to) that will show me all the information like you say. So in my case, I will have the song title and station letters scrolling across the display and then I can press the center button and nothing changes. I just have the song, etc scrolling with RDS to the left.

I figured RDS stood for Radio Display -something but I just don't see any changes.

 

I'm not sure what that is, then. I may have a different layout on my '12 Sport.

 

You know that volume knob in the center?
If you push the select button then twist the dial around it, that volume knob becomes the tuner and you can change the radio stations with it.

It will return to being a volume control about 10 seconds after you stop twisting it.

You can use it to select tracks on a CD.
Probably more than that, see your owners manual starting about p115.

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RDS is as described above:
Radio Data System (RDS) is a communications protocol standard for embedding small amounts of digital information in conventional FM radio broadcasts. RDS standardizes several types of information transmitted, including time, station identification and programme information.

https://en.wikipedia.org/wiki/Radio_Data_System

 

That "multi-function" knob in the 2nd gen. Fit was just awful. I could never get the hang of using it while driving-just too damn distracting! Maybe that's why I actually prefer the touch screen and steering wheel controls on my '15 EX (apparently I'm in the minority there).