Lots of advanced vapers like to spend time researching different tanks and trying to find out which one best meets their needs and will help maximize the capabilities of their mod. But many people, particularly new vapers, view this process as a chore. That's why many of the top manufacturers, including Aspire, Wulf Mods, Kangertech, and more have come out with kits to help make shopping for mods and tanks a little bit easier for everyone.
Kits help to simplify the buying process because you know for a fact that the tank that you are getting is designed to be optimized for the included mod. Some of the more popular kits include the Lone Wulf kit (a mechanical mod designed for advanced users), the Smok H-Priv 200W kit (phenomenal temp control setup), and the SMOK Alien kit (one of the coolest looking box mods out there).
Although these are "kits", they don't necessarily include every single thing that you need to start vaping right out of the box. You'll usually have to purchase batteries and battery chargers separately, unless you are purchasing a box mod that comes with an internal battery, such as the Conflict 50W kit. Of course you'll also need some e-juice to vape with, as these mod kits won't include any.