You wire it different ways. I just put mine in place of the factory one so it was powered by the same 110 (115) that the fridge is. It will 99% be 115V for you if you live in the US, Those across the pond would use the 230. 12V would be for a special case scenario on something with a 12V Supply.
Tap Room Hobo
I should have stuck to four fingers in Vegas.