Heh, ok, I can do some explaning.

If you used MacOSX's Finder in column view you can probably skip this though, since this is what this is supposed to be (and more).
The idea with this is to have some kind of grouping (or tree hierarchy - where the left is the parent of the one to the right). So, when you go to the right you go down into the tree. Music is a good example. Where, say, you have Genre at the top, and thus, this is put on the leftmost side. Genres consist among others of Pop, Rock and Trance. These are then inserted right of the Genre column. We have:

Col #1     Col #2    Col #3 ...
[Genre] -> Pop
           Rock
           Trance
[download]

Natrually, the widget is dynamic, so if we are in the second column, and pick for instance the "Rock" row, we can next to that (in the third column add/modify what we wanna have there), in realtime. Thus we can have:

Col #1     Col #2    Col #3 ...
[Genre] -> Pop       Queen
          [Rock]     etc
           Trance    ...
[download]

Myself is gonna use this for searching. And this is a good way grouping the result. And more to the point, really nice browsing through the data!