They're four demension figures. I watched a whole presentation on them and honestly the only significant uses they have are merely hypothetical(and those have to deal with physics and chemistry)
If you were ever to see a four demension it would expand, contract and, dissapear. I can't remember the exact reasoning behind it. I think it has to do with the way 3d figures look when they travel through a 2d plane, they expand and contract as well.
I posted a picture of how a hypercube is constructed. I found how it's made pretty neat.
http://en.wikipedia.org/wiki/Hypercube
It didnt seem too helpful but you can atleast see what they look like.