I mentioned this term the other day in a comment and was surprised to see it wasn't well-known. So allow me to explain.
When electronic cigarettes first appeared years ago they were quite a novelty, but they weren't as satisfying to smokers. The biggest complaint was the lack of "throat hit." They felt like drawing air through a straw, even though there was "smoke" in the form of vapor. It just didn't feel right.
When smoking a real cigarette, there is a feeling in the back of the throat when the smoke is inhaled. It's what made us cough when we first started, then our bodies got used to it. You draw the smoke into your mouth and then pull it all into the lungs at once. That's the hit.
Once the vaping companies perfected that (with chemicals, of course) the smokers got on board fast! The throat hit plus the huge volume of vapor released make it satisfying to cigarette smokers.
And that's what makes vaping to hard to quit, because now it feels just like smoking only without the smell and ash and dirt and grit. It's a much cleaner way to give yourself cancer, not to mention all the unstudied effects of pulling glycerin vapor into your lungs.