Variable Wattage - Wattage = Power. The higher the wattage, the more power to create more vapor. Higher-end e-cigs (vaporizers) give you the ability to control the power output. This is good because the optimal amount of power you want depends on the atomizer and the e-liquid you are using. For example, if you are using the Aspire Atlantis, you can use much more power than if you were using the Protank 2. Also, using more power will drain your battery faster, produce a warmer vapor, and use more e-juice.
Variable Voltage - Controlling the amount of voltage essentially does the same thing as varying the wattage. (Ohms Law). However, with variable voltage (VV) e-cigs you don't actually know what the wattage is.
mAh - milli amps per hour is basically an indicator of how long a battery will last. The higher the number, the more capacity it has and the longer it will last.
Display - LED or OLED displays are like a little computer monitor that show you important information about your vaporizer.
Charger Included - Indicates whether the c-cig come with a charger. Most e-cigs use a USB cable for charging.
Wall Adapter - Indicates whether the c-cig come with a wall adaptor. If you already have a wall adaptor for charging your phone, it should also be able to charge your e-cig.
Colors: R=Red B=Blue S=Silver or Stainless Steel BK=Black
Ohms - ohms is a measurement of resistance. Think of it like a pipe. The smaller the pipe the more resistant it is to water flowing through it. The bigger the pipe, the higher the flow rate. Atomizers (coils) that have a lower resistance allow more power to flow through them and produce more vapor. Coils that are below 1 ohm are called "sub ohm" coils. These coils require more powerful "high drain" batteries. High drain batteries are not only measured in mAh but also in amps. To use a sub ohm coil safely you should use a battery rated at least 25 amps. The lower the resistance (ohms) the more power will be used. "Cloud chasers" love huge plumes of vapor and use sub ohm coils and powerful batteries to get the most vapor.
Amps - Amps (amperes) is a measurement of current. The higher the amperage, the more power. Again, to use a sub ohm coil safely you should use a battery rated at least 25 amps.
Here's an excellent video that explains the difference between Watts, Amps, Ohms, and Volts
This video explains the two main ingredients in e-liquids: PG and VG