Note that it's just the mill attachment. You'll need to have one of those stand mixers to use it.
I've got something like that for my Kitchenaid, but if I remember correctly, it cost about half as much as the one you linked.
From the picture, it looks like there are 8 different settings. The description makes it sound like it's designed for baking, so I suspect that the finest grind is probably intended to make flour. The largest one is probably coarse flour.
The Kitchenaid one has 12 settings. Additionally, there's a part that you can tighten (or loosen) inside it so you have complete control over how fine/coarse you want to make it.
One caveat is that the top part is pretty small on mine (the one you linked also looks small), so I can't mill much at a time. I think there's also a restriction on how long to use it (don't want to burn out the motor). So it can take a fairly long time to mill a full grain bill.