How Electronic cigarettes work
The electronic cigarette is divided up into three main parts:

Atomizing device - When the electronic cigarette is inhaled, this heats up the
liquid nicotine turning it into a harmless nicotine vapour.
Battery - This powers the electronic cigarette. Each rechargeable battery lasts
for 2 - 3 days and you get two batteries including a power adaptor for charging
them.
Liquid cartridge - This contains the liquid nicotine which is turned into
nicotine vapour, giving you that instant hit. Once the vapour runs out, you
simply replace the cartridge. Each cartridge is equal to approximately 15
cigarettes meaning you can get 15 cigarettes for under 1 pound! The electronic
cigarette comes with 5 catridges equal to 75 cigarettes.
In automatic models, when a user inhales through the device, air flow is detected by a sensor, which activates a heating element that vaporizes a nicotine solution stored in the mouthpiece.
On manual models, the user must depress a button to activate the heating element to produce vapour which is then inhaled by the user. On most models an LED on the opposite end of the device is also activated during inhalation, which serves as an indicator of use. The LED's colour is usually a matter of preference, as the most widely used electronic cigarettes come with options for many different colours