[Max Lobovsky]

As several people stated, this is using a Peltier cooler, not a conventional compressor based cooler.

If you are familiar with the function of a thermo couple, a peltier cooler isn't too hard to understand. A temperature gradient across two different metals (they have to have some a large difference in some electrical property, i'm not sure exactly) creates an electrical potential and that's how you can measure temperature. Reverse the situation, and an electrical potential induces a temperature difference.