The mix
Play and compare
Space, the original, and Around you.
The round button plays and pauses. Space does the same thing when you are not typing in a field. What you hear is the same mix the export will render. If the song is set to be mastered, playback uses that loudness, so the finished level is what you hear.
Hear the original plays the untouched bounce. Back to the mix returns to the processed song. Use this whenever a slider has gone too far and you need the before.
Around you is a headphone preview. The browser places each audible part in space. The saved file stays a normal stereo song. It is not a surround master. Headphones matter. Speakers will not show it the same way.
The numbers next to the transport are where you are in the song, and how long the song is. A loop, if you set one in Pro, wraps the playhead inside that span.