C-x C-e evaluates the Emacs Lisp expression before the point. This gives the same result as the much more obvious M-x kill-emacs, but with the added fun of writing and executing Lisp directly in whatever buffer you're in. So to close the editor, we've written some code in a weird ancient language into some random text file, fired up an interpreter that's probably so portable you can run it on a 1980s toaster, and executed an expression which we had to make sure was wrapped in those vile parentheses everyone loves to hate.
Straightforward.
But I just had to explain my own joke, so I'll go wallow in shame for the rest of the day. :(
Pretty straightforward.