There are various versions of electronic cigarettes available, but they are all based on the same concept. Within the mouthpiece is an absorbent material that is saturated with a liquid nicotine solution. The mouthpiece screws on to the white tube, which is made of a type of metal. There is no need to worry about it getting hot and burning you though, as there is nothing actually alight in it. The only heated part of an electronic cigarette is the cartridge which contains the liquid nicotine. The heater runs off a lithium-ion battery, which can be recharged as often as you want in a wall socket or via an-car charger. It depends on the type of battery used, and how often you use it, but you can expect the battery to last for a least a couple of days before needing to re-charge it.
The nicotine solution in an electronic cigarette will, of course, run out over time, but the good news is that you can buy refills. Therefore, you do not need to keep buying a new electronic cigarette every week. As well as nicotine, the solution also contains either propylene glycol or glycerin. Though the names of those chemicals do not sound too friendly, they are actually not harmful at all, and are both commonly used in food additives. You can choose between a range of different concentrations of nicotine solution, depending on how addicted you are to nicotine. 4mg/ml is the lowest concentration, and 50mg/ml is about the highest. You should aim to steadily reduce the concentration of the nicotine solution that you use. Start off with a concentrate that works out equal to the number of normal cigarettes that you have been smoking (you can use a free online tool to do this) and then reduce the concentration of the nicotine solution used for the electronic cigarette on a weekly basis. It will depend on how much you are smoking now, but it is not unrealistic to be able to cut out your nicotine addiction within a couple of months.