The cuboctahedron is similar to the truncated cube in that the corners of a standard 3x3x3 cube have been filed down. On the cuboctahedron, this goes a bit further, making what appear to be additional faces.
You solve this exactly like the cube - no reason to be concerned by the apparent difference. Spotting cases is a little different but, once you work out which cube pieces are which, you can't go wrong.
These things seem to only be available on ebay. They go for some silly prices - if you look at the picture, you'll notice that mine is missing some stickers. I got this a little cheaper for that, I think. Sitckers were ordered but the fiddly little triangles mean that they are still waiting to be applied by someone with a steady hand and good eyesight.
If you have a Rubik's branded stand for your 3x3x3 cube, and your cube has solid pieces, you can make your own one of these and buy some stickers online. The triangle in the stand is at the angle you need to file the edges to - place it over the corners to see. Search for some advice before embarking on such a project and don't ruin a cube needlessly - even a manky old one - it's always sad to see a good puzzle meet a messy end.