First things first.
It will be a Linux Kernel(what else is new) running GoogleChrome on top. So it will be a platform we already know. The big bad web. No more service calls to the OS :D. It will essentially be a net OS for netbooks. Initially atleast. And then it will begin world domination. Lord save you. For a long time now I have been suspecting an evil empire rising.
As the faq of the matter points out, it will be free AND open source. The open sourcing will happen sometime later this year. The product will be available in the second half of 2010.
How does it change the world?
For good or bad, the world will change. The control buttons will change hands. Your life will be controlled by binary decisions (More than it is now). Your thought process will be controlled and directed to whatever the binary dictates. Do you think that is being too cynical? Wait and watch :D