Explaining Emacs to non-users is challenging. A first order explanation is that it’s a text editor but as we all know that’s a pitifully inadequate explanation. As you’re all aware, my default explanation is that it’s a light-weight Lisp Machine but that’s probably not very useful to anyone who doesn’t already know the answer.
Over at The Art Of Not Asking Why JTR attempts to give a simpler answer to the question. For him, as for most of us, the defining characteristic is Emacs’ configurability. JTR uses the metaphor of a coffee maker that not only brews your coffee but makes toast just the way you like it, orders coffee from your favorite roaster, and loads a crossword puzzle tailored specifically for you onto your smartphone. That’s Emacs. It does just what you want in just the way you want to do it.
With Emacs, your code becomes part of Emacs, virtually indistinguishable from the code that comes with the distribution. That means you have almost complete control over what Emacs does and how it does it. It’s hard to think of any other piece of software for which that’s true.
We all have our Emacs story and why we love it and JTR’s is a nice example of the genre. Probably no one but JTR will be completely satisfied with his story because, as I say, we all have our own.