An electronic cigarette is comprised of a battery, atomizer and a flavor cartridge. The battery is contained within the body of the ecig unit and is what powers the atomizer. E-cigarette batteries come in either automatic or manual models, depending on your preferred model of electronic cigarette. Automatic ecig batteries are powered when you puff on them; manual ecig batteries are triggered by a button located on the side of the body. The battery powers the atomizer, which in turn heats the e-liquid contained in the flavor cartridge; turning it into a vapor.