These stereoscopic images allow you to see the polyhedron in 3 dimensions. The two images are slightly different and correspond to what you left and right eye would see if you were looking at a real polyhedron.
This means you have to look at the left image with your right eye and at the right one with your left eye. You can do this by slightly squinting until the two images superimpose. 
The closer you are to the screen, the more difficult it is, so keep aproximately 60cm to it. It require some training, but it's worth the trouble.