It's no big secret that Netlify invented the term JAMstack. While it's possible to embrace the JAMstack without using Netlify, it's notable that Netlify is at the very heart of the whole "JAMstack landscape."
What does "JAMstack landscape" even mean? I like the term because it sets the stage that JAMstack isn't just this one thing, but a way of building sites by piecing together a bunch of different ideas, the most important of which is static file hosting. It's so important, I once jokingly called it SHAMstack. With static hosting at the core, it means that everything else you need to do can't rely on hosted server-side languages, at least not right alongside the production website on the same server.
So that's what "landscape" means. There are lots of companies, all involved in some slice of this pie. That's something that makes Netlify so interesting. You can use them for just about every slice of that pie, and it's a damn tasty pie (i.e. they do a great job of all the services they offer).