As most people up above said, particle board.
It's basically just a bunch of wood chips/flakes and sawdust mixed with an adhesive and squeezed together.
If it gets wet, the wood chips expand, and you get a swollen blister-like appearance. To much exposure to water, and it will swell to the point where it actually falls apart.
Before I worry you too much, It should be fine for a stand provided you don't let it sit in standing water. The coating/layer that gives it the wood-like appearance is pretty water resistant (maybe water proof, but it's easily damaged), so as long as you clean up any spills, shouldn't be a big issue.
The flat surfaces should be pretty easy to paint, but the edges are very rough. If you want the edge to match the face, you can buy strips of something (I forget what it's called) that stick to the end, I think they are iron-on (not sure, I've never used them before).
Otherwise, you could do a couple layers of something like a wood filler to fill in all those gaps.
What are your plans? if that's part of a manufactured stand/piece of furniture, usually there aren't exposed edges, they almost always but up against another piece (or are exposed on the back/bottom.