What is Emacs anyway?

I realised that not everybody may know what Emacs is, so I am adding a few quotes from famous Emacs users.

Emacs refers to a class of text editors, primarily for UNIX systems. Emacs editors are generally known for their large number of features, not all of which relate to editing text, and for its sometimes convoluted keyboard commands.

• Emacs is undoubtedly the most powerful programmer's editor in existence. It's a big, feature-laden program with a great deal of flexibility and customizability. As we observed in the Chapter 14 section on Emacs Lisp, Emacs has an entire programming language inside it that can be used to write arbitrarily powerful editor functions.

--Eric S. Raymond, The Art of UNIX Programming

• Don't get me wrong: Emacs is a great operating system - it lacks a good editor, though.

--Thomer M. Gil

• If you are a professional writer—i.e., if someone else is getting paid to worry about how your words are formatted and printed—emacs outshines all other editing software in approximately the same way that the noonday sun does the stars. It is not just bigger and brighter; it simply makes everything else vanish.

--Neal Stephenson, In the Beginning...was the Command Line

• I use emacs, which might be thought of as a thermonuclear word processor.

--Neal Stephenson, In the Beginning...was the Command Line

• I'm writing this article with software called Emacs. The program is unlike any other word processor I've ever encountered. In addition to cutting and pasting text, Emacs can run other programs; send electronic mail; browse the World Wide Web; retrieve, edit, and send files across the Internet; and keep track of appointments. It's like a digital Swiss army knife.

--Charles C. Mann, Atlantic Monthly