@sillyyak, since you wrote, in another thread, that you're "... not scientific, hated maths and crap at fiddly mechanical things ...", I'm going to expand a bit on
@Markw4mms comment, since you probably have no idea what the "center pin" is all about
Basics on how vaping mechanics works
Battery, switch, coil, wick, e-juice. Battery supplies power to the coil, just like your mains do for lightbulbs. Switch turns it on and off, just like a wall switch (only you have to keep it pressed for it to be on). When you press the switch: Current passes through the coil and the coil gets hot. Just like the elements of an electric stove get hot when you turn them on. The wick, which has absorbed e-juice, passes through the coil. The e-juice gets hot, and, like the water in a pan atop the aforementioned electric stove burner, vaporizes.
The coil, switch and battery form an electrical circuit. You can
kind of think of it like a pump and filter in a fish aquarium, which circulates water 'round and 'round thru tank and filter. When the circuit is "closed," or "completed," by pressing the switch: Electrical current runs around the circuit from the battery, thru the switch and the coil, and back to the battery.
This drawing illustrates it:
On an e-cigarette: The outside case of the battery and atomizer (aka: "tank") forms the "-" side of the circuit. The centre pin of the battery, the switch, and the centre pin of the tank/atomizer/coil forms the "+" side. The "center" part of the circuit connects to the "outer" part
through the coil in the atomizer, just like the lightbulb/resistor in the diagram above.
Everything else, all the way up to high-tech mods, are simply refinements or expansions of the above principles.
A bit of physics for the curious (you can stop reading here if you like).
Yes, for those who are wondering: The diagram is correct: Current really does flow from "-" to "+".
Electrical current in a DC (Direct Current) circuit flows because of an imbalance of electrons on one side, compared to the other. In our case: The "-" side of the battery is the side with the excess electrons. So, when the circuit is completed, the excess electrons try to get to the side with a lack of them: The "+" side. This imbalance, in a battery, is created by a chemical reaction of one type or another.