The basic concept of an Electronic Cigarette is a miniature smoke machine, except that the smoke produced you directly inhale and can possibly carry specific amounts of nicotine in the smoke.
The most popular Electronic Cigarettes are made up of 3 components, 1. rechargeable battery, 2. Atomizer and 3. Cartridge
1. Rechargable Battery: Most electronic cigarettes use a lithuim rechargable battery with a LED indicator on the tip that lights up when the cigarette is inhaled. They are also built with a micro processor chip. This tells the battery when the cigarette is being inhaled and to turn on.
2. Atomizer: The Atomizer is a miniature heating element that screws into the bottom of the battery. When battery turns on it heats up the atomizer to a low temperature which in turn vaporizes the water nicotine solution and creates the smoke.
3. Cartridge: The cartridge holds the water nicotine solution and is inserted onto the atomizer. With most brands of Electronic cigarettes, on average 1 cartridge equals 20 traditional cigarettes.
With all 3 components together you just puff on the end of the cartridge and it will produce a water vapor that you can inhale carrying nicotine in the water vapor so you can satisfy your nicotine cravings.