We have all sorts of starter kits that will be able to suit near any preference you have. Kits geared toward Clouds, Flavor, Nicotine delivery and everywhere in between.
MTL - Stands for "Mouth to Lung". The tightness of the draw will be the most similar to a cigarette. Typically a good option if you want to mimic cigarettes as close as you can. Don't care about clouds, just want your nic? This is for you.
DTL- Stands for "Direct to Lung". The draw is very easy and gives little to no resistance. These devices typically produce a much larger cloud. A great option if you want to stray from the cigarette style. Want clouds? This is what you want.
Internal Battery - These devices have their cells built in. they are designed to be plugged in to charge, often times just like your cell phone. Batteries are not removable.
External Battery - External battery devices have removable cells so you can swap them. Either for extra power during the day or allowing you to replace an old battery with a newer one.
Single Battery - Single battery devices utilize a single cell and have a typical range of up to 75w. These devices can be plugged in to charge the batteries safely, or on an external charger allowing you to always have a fresh spare battery.
Dual Battery - Dual battery devices utilize two cells (typically in series) to achieve higher outputs. up to ~200+w. They will give an increase in battery life, but not necessarily quite double the life. These devices MUST be charged on an external charger for longevity. On-board charging of batteries in series is RISKY. Extended use of on-board charging can lead to over-stressing of the cells resulting in an imbalanced charge on your device. This often results in the device/batteries failing. Many devices over-embellish their ability to USB charge. TL;DR, Only USB charge in an emergency.