Actually, it's both a lens AND a camera body simulation selection tool.
If you are considering the purchase of a lens, or just curious about the angle of view or focusing range of a given lens this tool is for you, regardless of what brand of camera gear you shoot.
If you shoot Nikon you can play even more with the ability to "play" with any combination of lenses and camera bodies Nikon offers.
This simulation tool allows you to select from both a DX or FX format, there are three images from which to choose, and you can zoom in and out to your hearts content to see if a certain lens and/or body is right for you.
If you come across a combination you like you have the ability to save it as well.
So give it a try, it's both fun and informative.