Jargon Buster: What is an Immutable Distro?
Quoting: What is an Immutable Linux Distro? —
An immutable distro is an operating system that cannot be changed and is read-only. You cannot make any changes to the core of the operating system (system files and directories).
Yes, you can add/remove files for storage and perform all the daily activities. And, the data will be stored as usual. However, any changes that require administrator-level topics just won't apply. Any system-level change will be temporary (if that happens) and the change will be lost after a reboot.
Immutable distributions also handle updates in a distinct way which involves an entire operating system being replaced with new components like a new installation instead of just the packages being upgraded.
Often, users confuse themselves that an immutable distro is something entirely unique. But, it is the same Linux distribution, it just differs in how it works/how it allows modification and updates.