Vaping is the process of inhaling vapour which contains (in most cases) nicotine.
Vaping is all about harm reduction for people who smoke cigarettes/tobacco.
With vaping there is no combustion (burning) and hence no smoke, which is very harmful when inhaled. Instead, an e-juice (usually containing nicotine) is heated up to the point where it is vapourized (like steam in a kettle) and this vapour is then inhaled. This vapour is infused with some of the elements (such as nicotine) from the e-liquid.
There are 3 base components in the liquids used for vaping, namely: Vegetable Glycerine, Propylene Glycol, and Nicotine. Flavouring is also added to give the resulting vapour a pleasant taste.
Nicotine by itself is not a known carcinogen. When smoking tobacco/cigarettes thousands of chemicals are released when it is burned; many of these chemicals are harmful and some are carcinogenic. Vaping reduces the harm by using nicotine without all the other harmful chemicals found in tobacco smoke and by avoiding combustion altogether.
Even though more research is needed to prove exactly how safe, or unsafe, vaping really is, just by understanding the differences between vaping and smoking it is quite obvious how much less harmful vaping is when compared to smoking tobacco/cigarettes.