Basically it narrows a search to show all elements linked to that hyperlink. In the above example, by clicking on Jack Johnson, only Jack Johnson related albums would appear. For that matter, if I moused over the year or the genre or the album title, all related material would appear, to the exclusion of other artists / albums that listed in the initial search. It is a 'nice to have' as you could refine your search in fewer mouse clicks / key strokes, in a more efficient way then typing the exact phrase or artist in the initial search pane. About half the 'other' music player do it (for eg Microsoft Media Player, Media Monkey etc)