It forces the browser to use hardware acceleration to access the device’s graphical processing unit (GPU) to make pixels fly. Web applications, on the other hand, run in the context of the browser, which lets the software do most (if not all) of the rendering, resulting in less horsepower for transitions. But the Web has been catching up, and most browser vendors now provide graphical hardware acceleration by means of particular CSS rules.
Using -webkit-transform: translate3d(0,0,0);
will kick the GPU into action for the CSS transitions, making them smoother (higher FPS).
Note: translate3d(0,0,0)
does nothing in terms of what you see. It moves the object by 0px in x,y and z axis. It's only a technique to force the hardware acceleration.
Good read here: http://www.smashingmagazine.com/2012/06/21/play-with-hardware-accelerated-css/