The Rubenking cube is a sticker variation on the standard 3x3x3 cube. It was invented by Neil Rubenking. The same six colours are normally used. Opposite faces have the same two colours and the stickers create a diagonal line across each face.
The sticker pattern is incredibly confusing once you've messed this bad boy up. You solve it like a cube. I use the same centre rotation algorithms for this as I do for picture cubes and the pillowed mastermorphix. I find it hard to concentrate when the centres are rotated and have to sort them out early in the solve. You can also do this at the end if you prefer.
Rather than look for this type of cube to buy, it's easier to order the stickers and make one yourself out of a manky old cube. The one I bought isn't stickered correctly and I've never bothered to change it - no need to point this out to me if you've spotted that.