Re: "Serverless" is a marketing term. No more, no less.
Well, I have to disagree a bit: I am running a backend for my mobile app on aws Lambda for about 4 months now (https://itunes.apple.com/us/app/procast-podcast-app/id1215380730).
The app stated growing quite rapidly recently, and the scale I get from Lamda is amazing. And the cost is just a fraction what I would spend otherwise. I architected it with quite some caching tricks to save some money, but even without that is it truly amazing. And I say that in spite of working on the Microsoft Stack for more than 15 years.