This image is in Stereo. The slight differences allow you to see it in 3D. The easiest way that anybody can do is to do the whole 'magic eye' thing with it. Stare directly into the middle of the image and pretend that you're looking at something between you and the monitor. There, 3 Dimensional!
You can also view this image in 3D with shutterglasses, shuttergoggles, a polarized projector, a 3D LCD monitor, or an expensive headset.