Devices can include individual mods which either take external batteries or have built in batteries. They range in size and shape, but they also range in power. The higher the power used (wattage) the more vapor produced.
Some devices are full kits - meaning they come complete with a device and a tank.
Pen styled devices refer to their shape and are usually non-adjustable and a single button operation. These can be perfect for beginners, but because they are not adjustable, you cannot customize the way it vapes to fit you. If it's not enough vapor or it's too much vapor - there really isn't anything you can adjust, unless there are different resistance coils that can be used.
If you have any questions regarding any device please read the description in full - if that doesn't help or if you have any additional questions, don't hesitate to contact us and we will gladly assist you.