What is the thing that people are vaping? See detail.

It is called ”e cigarette”, but it’s not tobacco related, Added:except for the nicotine (the kind with nicotine). So what is the item being vaped?
I went here:
https://www.wordhippo.com/what-is/another-word-for/e-cigarette.html
but it just gives me the short form, “e-cigs”