What is Chrome?

Google Chrome, developed and controlled by Google, may refer to either the web browser or the OS that uses the latter web browser as its GUI. Chrome OS is intended for laptops (not intended for desktops), which Google markets under the name Chromebook. Just like Google's portable OS, Android, it is also based on Linux.

By Source (WP:NFCC#4), Fair use, https://en.wikipedia.org/w/index.php?curid=65277366

As of 2010, a year before its first release, the development of the Chrome OS switched to Gentoo because of the flexibility of its package manager — Portage.

Although the OS is open source, users only have access to personal files, but no access to system files especially the kernel. Chrome OS mostly runs web applications making it basically a thin client — except for multimedia with several (if not all) codecs, camera and daemons.

Running Chrome OS (stable channel only) demands the user to completely trust Google as it controls all aspects of the OS including and perhaps not limited to updates, which is perfect for users. As a matter of fact, all applications are only accessible through the Chrome Web Store and there is little to no risk of viruses or other malware.

As of version 53 of the OS released on September 2016, Google Chrome can run a Google Play, which allows users install and run Android apps.

Chrome OS has a limited shell in user mode named crosh.

The latter was taken from help_advanced.

Installing Chrome OS:

There is no OS installation. Chrome OS is heavily isolated. In other words, the user has no root access — no control over the OS.

In case of extreme errors, there is a local utility that resets the system to factory settings from an on-board ROM chip called POWERWASH. Another alternative only when suggested by the Chromebook vendor is to re-store the OS creating a recovery USB flash drive and booting from it. In the latter scenario, you need to contact the vendor for specific instructions.

Note that OS updates do not count as installations. Updates are pushed by default and the end user only needs to reboot the machine. These changes to the OS are written to a ROM chip. If you were to run POWERWASH, you would not have to reinstall all updates to the OS.