Let's suppose John builds a web application for weather updates. His backend application creates HTML pages that show the weather, then sends those pages to the user. However, the web application is somewhat slow.
On the other hand static HTML pages were one among first things on the internet, and Jamstack is not really an ultimate inovation in my opinion but only a better way to implement older concept as a new product. Also, Static HTML sites can be easily built without entering into Jamstack tools.
Title might be misleading as one might expect more basic fundamentals of Jamstack, not actually diving into one of several Jamstack tools without much info, and here's why:
Jamstack allows developers to quickly create and service websites.
Not entirely true, as Jamstack is arhitecture on top of another product which one should learn first - think about inexperienced developers first. Also, any inexperienced developer who's not familiar with Jamstack wouldn't benefit much as you didn't explain your code at all.
...containing all essential information...
Well, also would disagree, based on my previous words. If you want to give essential information, it's not by diving into one of several Jamstack tools and show some unexplained code, but rather on which occasions would Jamstack arhitecture be good for a user considering all that Jamstack offers. There's pros and cons for everything. Best tool for an app/website is often not the easiest one, it takes more consideration.
Essential info would be
As you stated, Gatsby is react based one. But, what is React?
Same thing you have with Next.js which is also React based. Grindsome and Nuxt.js are Vue based. There's another one called Scully, which is newer and 1.0 release was this year - Angular based, tested it, works great.
I hope this gives you idea for more and better content on this matter.