The upper left panel, of course, shows the track that is playing. The center column is for the artists - listed in either alphabetical order, or the order in which Scan Disk encounters them on the disk (which starts out as the order they were added to the disk). When you click on an artist in the center column, all their albums appear in the upper right corner panel. When you click on one of those albums, all the tracks for that album appear in the lower right panel.
I think one of the reasons it's set up that way is so that you can browse for what you want to play next while a song continues in the upper left panel. Works well for me.