ChromiumOS is the operating system that Google ChromeOS is built on, which powers Chromebook laptops and ChromeOS workstations. The OS is all about the web. All apps are web apps and the entire experience takes place within the browser, so users do not have to deal with installing, managing, and updating programs. Each app is contained within a security sandbox and the OS verifies the integrity of its own code every time it is restarted, making it harder for malware and viruses to infect the computer. Most of all, ChromiumOS is obsessed with speed. It takes out every unnecessary process and runs everything it possibly can in parallel, allowing users to go from turning on the computer to surfing the web in a few seconds.
Many Googlers use Chromebooks and ChromeOS workstations as part of their daily work.