Mozilla's experimental rendering engine, written entirely from scratch to avoid a lot of the problems that Gecko and other engines have because of their age. Along with that they're experimenting with parallelized layout and other things to get better efficiency and performance.
Mozilla is (planning on) using it for FirefoxOS. They have no plans to do so, but I'd be happy seeing it in desktop Firefox.
edit: planning on
FirefoxOS uses Gecko like desktop.
I spoke too soon. They are planning and working on it.
Yea once it's gotten to where it's stablish and can render most websites I'm really wondering how hard it'd be to start making it work on the desktop as a replacement. I know there's the whole XUL issue but I'm betting that's solvable since they don't have XUL on mobile/firefox OS either.
A small electric engine, I believe. In this case probably a play on how we call web renderers "browser engines". Servo is Mozilla's next-gen browser engine.
The name actually comes from Tom Servo from MST3K (whose name in turn probably comes from the motor)