That's a tesseract (4 dimensional cube). What you see now is the shadow of it's shadow (every "n"th dimensional object casts an "n-1" dimensional shadow.), so it's impossible to make out what is actually happening, but it's rotating on an axis which exists on all 4 dimensions.
It's a large cube with a smaller one inside with diagonal edges linking one vertex of a cube to the other cube. When you try to follow an edge of the biggest cube, one edge that links one vertex of the biggest cube to a vertex of the smallest one tricks your vision, making you follow the diagonal edges instead of the edge you were following before. It is hard to explain for me.
I prefer ynvaser explanation, although I haven't learned about 4th dimension yet.
EDIT: Wait, now I got it.