A Quine is a program that outputs its own source code. Named after a concept by Douglas Hofstader, Quines are a demonstration of Turing Completeness.
Javascript being a Turing Complete language, it's possible to write a Quine in JS, but obviously the whole thing is a bit of a challenge in any language, because it's difficult to think around the problem - each change definitively changes the output and the source at once.
quine.js simply reads it's own source code and echoes it out. It's kinda cheating, but it actually works, so in a sense it's not.
I'm not counting it as in the spirit of a Quine though, so:
Uses an IIFE style implication to echo out an implicitly converted function to the console.