Maybe this will shed a little light on things. When KDE4 (4.0) was introduced, they got rid of the concept of storing icons on your desktop. You could place "widgets" on the desktop, but not traditional "icons". Many traditional users did not like this and wanted the ability to have traditional icons on the desktop. So the concept of a "folder view" was introduced in a subsequent release. Since the desktop is actually a folder (even in MS Windows), the devs made the "folder view" a lot more flexible in that it can display the contents of any folder. Although this was a step in the right direction for traditional users, it was still not quite the same. So... the devs introduced the ability to use a "folder view" as your desktop. This, in essence, duplicated the functionality of the traditional desktop.
With the in mind, tschommer is right. You can either place a "folder view" widget on your desktop (as shown in your picture), or you can set your whole desktop as a "folder view" activity. Also, you can indeed place a "folder view" widget on either type of desktop (be it the new KDE4 type desktop or the folder view as desktop). Hope that clears it up a bit. It took me a while to get it down.