First it should be mentioned that e juice, vape juice and e liquid are all terms to describe the same thing. It’s a fluid used in vape devices that creates vapor. Similar to the heated water, vape juice can be heated between 90℃ and 200℃ which turns it into vapor that you then inhale. In fact, vaping liquid is a mixture of water, nicotine (but not always), propylene glycol (PG) or vegetable glycerin (VG) and food grade flavoring. Vape juice often comes in a variety of different strengths of nicotine. Take the Frostbite 100 ml as an example, 0mg, 3mg and 6mg are available for your option. The strength you choose depends on your individual tolerance. The heavy smokers who switch to vaping for the first time may tend to choose higher concentrations of nicotine. For vapers who smoked only a little amount before switching to vaping are more likely to choose zero or low nicotine e liquid. The best way is to experiment and see which nicotine strength works best for you. Normally vapers should start with a lower level and moving up. Propylene Glycol is a substance used in many flavorings to help distribute the taste and any food grade flavoring evenly throughout the liquid. Vegatable Glycerin is a sweet, thick, vegetable based liquid. Normally a combined e liquid of PG/VG is recommended. Most of our e liquid have mixes containing 70% PG/VG 30% to 50% PG/VG 50%.