Where to find documentation on macOS file system structure?

If you want the most accurate and current information about macOS’s file system structure — including APFS (Apple File System) volumes, containers, snapshots, and virtual volumes — the best place to start is Apple’s official developer documentation. The Apple Developer site has a section specifically on APFS and File System Fundamentals:

• Apple Developer Documentation – File System Programming Guide
• Apple File System Reference

Beyond Apple’s own material, you might also look into Jonathan Levin’s “macOS and iOS Internals” series — particularly the volumes covering the file system and kernel architecture. They provide in-depth technical explanations of how APFS containers, data partitions, and system snapshots interact in macOS.

The Eclectic Light Company has run a few articles on security changes in recent versions of macOS – including the division of startup volumes into a "sealed system volume" and a read-write volume that first appeared in Big Sur.

https://eclecticlight.co/mac-problem-solving/

Another source

It details the Difference between Intel Apple Computer and Apple Silicon Machines visa vie Drive Structure

https://eclecticlight.co/2021/12/16/boot-disk-layout-in-macos-monterey/

Unless you’re a developer, detailed info is difficult to come by.

Not particularly technical, but probably a couple of good places to start:

Disk Utility User Guide for Mac - Apple Support

Use the Finder on Mac - Apple Support

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