Chromium is the name we have given to the open source project and the browser source code that we released and maintain at www.chromium.org. One can compile this source code to get a fully working browser. Google takes this source code, and adds on the Google name and logo, an auto-updater system called GoogleUpdate, and RLZ and calls this Google Chrome.
I was kidding about stealing but, everything new in chrome comes to chromium 1st except the google tracking stuff.
as fast as chrome is i think chromium is a little faster on a linux machine.