E-cigarette or electronic cigarette is a battery operated device which aims to provide the sensation of smoking minus the actual smoke.
They come in a range of shapes. Some look like USB drives and others look like pens and of course it also available in the cigar shape. You can see them at RELXbyCaker.
The aim is to reduce the dependence on actual tobacco based cigars.
Basically it emits a vaporized solution to inhale and that solution usually contains nicotine.
So the smoker still gets the nicotine minus the more harmful smoke.