I guess I'm just not sure what these do?
Does it change the look at all on the wheels? Does anyone have a before/after pic of these?

 

They put the wheels farther away from the vehicle. They create an extention from the rim to the hub.

 

I have them, they make my rims flush with the fenders rather than being stuffed under them and making it look like a narrow trac. Add a lil bit bigger tire and it sticks out just slightly enough to look AWESOME!

 

Well good, I like the wheels sticking out. Does it do anything mechanically speaking?

 

No, not when installed correctly. It's like bolting a thick disk to your hub, then bolting the rim, to the disk, which is bolted to the hub. So, from the outside of the Jeep to the center it would be Wheel>Spacer>Hub

 

Spacers are not just for looks...
They ARE needed when running wheels that do not have the correct backspacing. Take for instance your stock wheels. If you have a wider tire on the stock rim they will/can hit the lower control arm when at full lock. So you either need to buy new rims with less backspacing or get spacers to decrease your backspacing to run wider tires.