When you use a electronic cigarette, the act of puffing on the cigarette, triggers a electronic sensor inside the ecig that tells the battery to charge up a heating element inside the cartomizer and vaporizes the propylene glycol mixture which contains nicotine and a few other chemicals.
The result of when this nicotine solution is vaporizes is the creation of a water based smoke. It looks like smoke but it is not.
This smokeless water vapor contains nicotine. It disappears very quickly. It doesn’t cause your teeth to turn yellow. Those around you who inhale the water vapor do not get lung cancer because it is not second smoke.
Because this smoke look a like water vapor does not odorless, it does not leave your cloth smelling like a pack of cigarettes because there is no tobacco, ash, or any of the dangerous chemicals inside a normal cigarette.