Unlike smoking, which uses combustion to create an inhalable smoke, vaporization heats up a substance to a specific temperature to create an inhalable vapor. In an e-cigarette, this is accomplished by the coil, which receives power from the battery to heat up the e-liquid to the point of vaporization.
The rate in which the coil heats up can be controlled if you have a variable wattage device, with more power equating to a hotter coil. Running your coil at a higher temperature will produce vapor more rapidly and will help the device produce more dense and large clouds of vapor.
You can read about the differences between vapor and smoke HERE.