Nope, it's a place to see all things in the scene that are of one type in one place, and adjust the most commonly adjusted settings etc. So you get to see all lights in a scene (lights, light materials, suns, skies), all displacement from all materials in the scene, all cameras in the scene, and so forth. Saves you hunting through the scene explorer to find them all, and let's you do things like turn off all displacement for testing (well, displacement materials), or check the settings of one light against another and then adjust, or see all scatters and change the display mode of each or turn some on and off, and so on and so forth.
(So you were almost right, only you don't pick what it shows, it finds and shows everything in the category for that tab automatically)
