I read a little more about it. The science behind it is simple. The hot makes the metal expand and the quenching with cold makes it contract very fast.
Unfortunately the paint cant hand the extreme temperature changes and starts to crack and peel. So not exactly the best way to go about fixing dents.
I did see another tool which I am interested on getting my hands on since my paint is pristine but I have like 15 nickel and dime sized dents...
You can search pdr on youtube and see more.