Both of Google's extant operating systems, the Android OS for mobile devices and Chrome OS for chromebooks, are based on the Linux kernel. In case you haven't heard, though, Google has another operating system under development—and it isn't based on Linux. Google says the so-called Fuchsia OS is meant for "modern phones and personal computers with fast processors [and] non-trivial amounts of RAM."
Fuchsia is built upon a new microkernel called Magenta that is loosely based on the "littlekernel" embedded kernel. Using a microkernel means that Fuchsia can neatly sidestep some of the issues that have plagued Android devices, like slow updates for device drivers. The new kernel is also a huge flying leap into the unknown: unless hardware vendors pile on their support, the devices which can run Fuchsia will be limited. So far, Fuchsia supports x86 PCs as well as Qualcomm's Snapdragon 835 SoC.
Google has likely been working on the new OS since early last year, but the first public release of Fuchsia was this past August. At that time, the OS was little more than a command line and a few test applications. Recently, Kyle Bradshaw over at Hotfix IT wrote up some instructions for how to build a copy of Fuchsia and its new demo interface called Armadillo. You can check his video above showing off the UI for the operating system, or hit up Ars Technica for a full preview of what Fuchsia could look like on smartphones.
It's not yet completely clear what Google intends to use Fuchsia for. The OS could be a replacement for Android, Chrome OS, or both. It also could feasibly be intended as a competitor for Microsoft's Windows, although any such aspirations are likely far down the road for the fledgling system. We could speculate for days on Google's intentions, but at this early stage it seems more prudent to simply wait and see where Fuchsia ends up.