The idea behind thermoelectric cooling (TEC) is that you can use energy to actively move heat from a cold place to a hot place. Generally, this isn't the case: the temperature in a room will reach equilibrium unless you do work (spend energy) to change that; if that sounds familiar, it's because it's a law of thermodynamics. A Peltier device is a cool (no pun intended) little gadget that facilitates this kind of cooling. When you send current through this white plate, one side becomes very cold and the other very hot.