If you're talking about the smoking kind, it heats up pot to a point where the THC is released but not to the point of combustion. When you're finished, most of the plant material is still in the bowl. And almost no smoke is produced. It's a MUCH healthier way to get high. It's a trip the first time you try one. You take a hit and you're so used to the harshness of the smoke in your lungs and you're going "this is gay" and then POWIE, it hits you.
