The main difference between vaping and smoking is that smoking delivers nicotine by the process of burning tobacco which causes smoking related health issues. Vaping delivers nicotine by heating a liquid in a less harmful way.
Harm To Health
Smoking is extremely bad for your health because it generates bad toxins as a result of burning the tobacco. Some people try to cut down smoking as a step towards quitting. Vaping is not harmless, however, it is a lot less harmful than smoking. The healthiest option is to not vape or smoke. Do not vape if you do not smoke, only use vaping as a tool to help you quit smoking.
Nicotine
Smoking delivers nicotine and vaping gives you the choice whether to have nicotine or not. You have the choice of which concentration of nicotine you would like. Vaping delivers nicotine via an e liquid which is a much less harmful way.
In a cigarette, the amount of nicotine is generally fixed and delivery depends on how you smoke. In vaping, the amount of nicotine is dependent on the strength of the e liquid that is chosen, and how you vape.
It is also important to note that nicotine is addictive, it does not cause cancer.
Feel
Vaping is not the same as smoking. Some people find vaping works in order to help them quit because it offers similar experiences to smoking a cigarette. Vaping provides sensations similar to smoking a cigarette.