Comment by bayindirh

Immutability means you can't touch or change some parts of the system without great effort (e.g. macOS SIP).

Atomicity means you can track every change, and every change is so small that it affects only one thing and can be traced, replayed or rolled back. Like it's going from A to B and being able to return back to A (or going to B again) in a determinate manner.