A very old skool editor which has survived to become a power-tool.
Philosophy of Emacs is a tiny core in C which manages a buffer of text, but includes a scripting language EmacsLisp out of which can be built almost any tool or functionality imaginable.
Much of Emacs's core functionality is built in Emacs Lisp. And then others have added lot more.
There's a long history of writes and re-writes, but the most common version today is the one that was largely written / launched by RichardStallman as a flagship Gnu project.
Is Emacs a Lisp machine?
But it is the closest that many of us are likely to get to actually having a Lisp Machine.
Emacs is, yes, a powerful platform in its own right that can be scripted in Lisp "most of" the way down.
The ideal of a Lisp machine is that it's Lisp all the way down. And open and inspectable all the way down.
There are a couple of images of Lisp Machines around that can be run on obscure hardware. I don't know if anyone has packaged them sufficiently well into a VM or container to be usable.
So there are no practical Lisp Machines.
But Emacs is pretty widely used. And people are building new and useful software on top of it. Things like OrgMode show that the community is still active, vibrant and innovating. Plausibly Emacs is a platform which will have some cutting edge powerful new applications built on top of it for years to come.
So, it's about as close to a Lisp Machine experience as you can usefully get today.
The only other thing which is kind of like a Lisp Machine is Smalltalk. It's the same - copen, inspectable, written in the same language all the way down- live system.
It's just not Lisp. But it is another elegant, minimal language, partly inspired by Lisp and the ideals of Lisp. But it's a different language.
Quora Answer : Why does Emacs come with modes for useless programming languages, such as Modula-2 and Prolog, instead of useful languages such as Go, Rust, or Clojure?
Those modes got written when those languages were popular.
In practice, Prolog is an obscure but still very relevant and exciting language. And it's great that Emacs supports it.
I'm not really bothered about Modula-2 but I guess some people are.
I'm a passionate Clojurist though. And while I'm not sure if Emacs comes with Clojure out of the box, there's plenty of support for it. (It's just another Lisp, after all).
I use Sam Aaron's Emacs Live collection of plugins which gives me a very good Clojure experience in Emacs.
I have no doubt that there are modes for Go and Rust if you know where to look for them.