I’m such a Mac user that I don’t even get it. I am simultaneously laughing at myself and embarrassed.

MacOS create these directories to store metadata. But because it starts with a dot, you don’t normally see it.

macOS only does this on network shares or external storage that’s formatted in neither HFS+ nor APFS, Apple‘s file system formats.

Right, so anything that might be used with other machines.

ZIP files created with macOS‘ file manager Finder can also contain DS_Store files.

Yes, the idea is to support macOS features on non native file systems.

If you want to look it up, some of this goes back to HFS, a file system with a resource fork and data fork. It allows you to do pretty cool stuff.