Some people put specs and compare and see who has the best build or setup or whatnot, but Im not really one of those. There are forums out the waazoo about vaping, mods, attys, fluids and what not. There are hundreds of facebook pages on vaping, they range from what type of vaping, to the region you live in or coil builds.
Vaping can be very segmented. E-cigs come in many different styles with many different components or very few. A typical starter kit can consist of the tank, a battery, charger and fluid. A more advanced setup can consist of wire for making coils, wicking material, atomizer or tank, mod, battery, drip tip or chuff cap, and charger.
Atomizer/Atty/Tank
The atty is where fluid is heated, atomized and turned into the aerosol to be inhaled. There are two basic types, tanks, and drip atomizers.Tanks have some sort of reservoir for holding e-liquid. Sizes vary from a few mL, upto 6mL. Inside the tank is a "coil" or "wick". They vary in electrical resistance, size, and interchangeability between tanks. Some tanks have coils that are not intended to be rebuilt and must be replaced. Other tanks have rebuild able coil. Drip atomizers come in many different styles, ranging from simple, cheap and disposable to large, expensive, and rebuildable. They can have a single coil, dual coil, quad coils, serial, parallel coils, and twisted or strand. The building of coils for atties has become an artform all its own. Just checkout reddit.com/r/coilporn. This is a SFW site.
Mods/Batteries
Mods are what hold the battery whether its a mechanical mods, box mods, or varible voltage/ wattage mods. Mods can also fall into multiple categories. Mechanical mods are defined by a mechanical button used to complete the circuit required to fire the e-cig. There is no adjusting the volts, wattage, or current that is sent to the atomizer. They are cylindrical in shape, and resemble a AA battery flashlight. Box mods come in several different varieties. They are box shaped, as the name implies, usually have an IC built in that controls wattage or voltage or both. There are some box mods that can also be mechanical, but these are generally hand made, one offs. Then there are variable voltage/wattage mods. These can resemble thinner versions of the mech mods. EGO style batteries are fairly popular starter mods. The batteries are rechargeable but not removable as the tube is the battery.
This is just a quicky on E-Cig. I will answer what I can, or point people in the right direction when I cant.
Here are some good sites for futher or more detailed reading.
http://www.e-cigarette-forum.com/forum/