Heres a video by Inlife Electronic Cigarettes,  explaining the working of an electronic cigarette:

Visit our YouTube channel to watch more videos

The Electronic Cigarette comprises of a rechargeable battery, an atomizer and a cartridge that comes in varying degrees of nicotine content.The cartridge contains, water, flavor, nicotine and propylene glycol (a safe food additive). When the user inhales at the mouthpiece, a small switch located in the battery is activated and power is delivered to the atomizer. The atomizer then creates a vapor derived from the moisture and propylene glycol that is found in the cartridge. As the vapor passes through the cartridge, it picks up the nicotine and flavoring and delivers it to the user.