That's great! I'm glad to hear it wasn't an RI.

Now onto your thermostat question... they work by regulating the power input to a heat source in order to maintain a set temperature. You just plug in the heat source to the thermostat, plug the thermostat into a wall outlet, place the probe near the area that you want to regulate, then set the thermostat to the desired temperature. The on/off thermostats are usually used to heat rooms with a space heater, but many people use them for their cages because they are a little cheaper. The proportional thermostats are usually used for cages and they regulate the amount of current that goes to the heat source such as an UTH or heat rope. They're better at keeping a more consistent and accurate temperature within the enlosure, but the on/off ones work fine, too.