I am starting to work on Peltiers....

I am kind of confused on how they work. So, we heat (or cool, depending on your perspective) by applying DC current. To get the opposite effect (to cool when heated), we apply negative DC current.

Here is where I am confused... Most peltier controllers use PWM, so that is not DC current. Correct me if I am wrong, but PWM chips (like the one found on MegaMoto) output PWM.

Are we relying on the avg current to dictate the temp of the cooler? In other words, the faster the PWM goes, the more avg current is going into the cooler and vice versa. So, effectively, we are turning the peltier off and on at some frequency to get the temp we want to achieve. Is that correct?