Chromebook
Chromium OS | Performance Issues | Security | Learning More

Chromebooks run Chrome OS, a Linux-based operating system designed by Google
While Chromebooks offer a less expensive computing experience, it is essentially a cloud-based operating system though they can work offline, syncing when reconnected to the Internet.
Initially designed to rely heavily on web applications for tasks using the Google Chrome browser, Chromebooks have since expanded to be able to run Android and full-fledged Linux apps since 2017 and 2018, respectively.Chromebooks can work offline; applications like Gmail, Google Calendar, Google Keep, and Google Drive synchronize data when reconnecting to the Internet. Google Play video content is available offline using the Google Play Movies & TV extension with the Chrome browser.
— Wikipedia
While most of your data is stored on Google Docs, there is a SSD hard drive like in most modern laptops.
Chromium OS

Chromium OS is an open source version of Google's Chrome OS.
Chromium OS is an open-source project that aims to build an operating system that provides a fast, simple, and more secure computing experience for people who spend most of their time on the web.
— The Chromium Projects
Google released the Chromium OS open source project in 2009.
Performance Issues
ChromeBooks are generally running on much less powerful hardware than their Windows equivalents. This is possible because so much of the computing is done remotely, in the Cloud via the Chrome browser and operating system.
While the computing performance may be compensated, this does not extend to the user experience of embedded hardware like cameras and video cards.
This evaluation of a ChromeBook supplied by an American school district lists some significant shortcomings:
But what I quickly discovered is that the Chrome's sound output, camera quality, and screen are inferior to our Windows-based home PCs.Our kids have been using Chromebooks in school for years and pretty much hate them because they're just, well, cheap. Poor keyboards, tiny retina burning displays, ads, ads, ads and oh yeah, ads! — AskWoody
I'm sure there have been upgrades and options for better ChromeBooks. Just be clear on what you're getting if you purchase one.
Chromebooks may be suitable for light users, but any power user should look elsewhere.
Security
Chromebook is promoted as safer than Windows because the applications are being run sandboxed in the cloud.
That would be great if Chrome had no zero-day vulnerabilities (unlike the Chrome browser) and the cloud wasn't being hacked all the time.
Unlike traditional operating systems, Chrome OS doesn't trust the applications you run. Each app is contained within a security sandbox making it harder for malware and viruses to infect your computer.
Yes, it is harder in a sandbox, what if the server is hacked? Remember, the cloud provides 24/7 access from anywhere in the world and is almost never shut down.
Privacy Issues
ChromeBook has considerable privacy issues (Google never forgets) but will run Android apps, which may appeal to those with Android devices (as Windows 11 is supposed to do).
Chromebook® is a registered trademark of Google.