That Amazon listing appears to be a bit misleading.
Unless I'm somehow mistaken, what was shown in the Amazon link is essentially a lens filter. You screw it onto the end of another lens. While I've never had or used one from what I've read on them is that they're extremely low quality (which you can assume from the price) and more novelty than anything. If you have $20 that is just absolutely burning a hole in your pocket and can't think of any other use for, you'll only be out $20 but don't expect anything worthwhile out of it. Personally I'd save the money for gas, food, or save it to put in the lens fund for a real macro or fisheye lens (the two cannot be combined).