You can change the default action associated with the Play triangle icon (the “One Click action”) in the Play preferences settings. See those three horizontal line icons on the right of the list? They are drag handles. You can click and drag (or touch and drag on a Touchscreen device) to change the order of the list. The topmost item is then the default action, as Brian says.
It means that you have three versions of that song (Behind the Mask) in your local library and that there 33 versions available via the streaming service you subscribe to.
There is one that I have been trying to find the meaning of. It is sort of a funky elongated “s” shape with a number after it. I tried to google “roon sigma symbol meaning” and didn’t find much that made heads or tails, so I can’t speak to if it were useful output or not. If I see it again I will try to grab a shot of it. Think of an ascii rendition of something like a sigma sign.
Btw…dudes who are writing and supporting Roon, good job guys. This is REALLY cool. I am loving the ecosphere of this. Up until about 4 months ago I detested digital but a friend got me to try a wiim pro plus…man was I hooked. Then I looked to try and better that and ended up with a new (affordable) dac and roon. Again, this is really very cool indeed.