FireFox OS is an operating system for mobile phones. As you would expect, with the FireFox name attached, it is an open source effort derived from “open web standards.” The project was announced as ‘Boot to Gecko’ in July 2011, renamed to FireFox OS in July of this year, and is expected to appear on physical handsets next year.
The OS is still in the fairly early stages of development, but so far it consists of three layers - Gonk, Gecko, and Gaia. Gonk is a UNIX kernel, which shares some elements with the Android OS. Gecko is the application runtime, and implements support for HTML, CSS, and JavaScript. Finally Gaia is the user interface layer, and is written entirely in these same web technologies - hence the “open web standards” angle.
Any new phone OS is going to have its work cut out to battle the dominance of Android and iOS (just ask Microsoft), but at least Firefox OS is trying something slightly different. One of the big things the operating system hopes to achieve is to break the dominance of the Apple app store. Apps for Firefox OS are written in standard web technologies and can be run on any platform. Many see this as an important step as mobile devices become the dominant method of accessing the web and Internet services. FireFox OS might not replace the likes of iOS in mainstream use, but it will doubtless give rise to some interesting and important discussions.