Understanding file permissions and access modes of Unix-based systems is not one of the top priorities of day-to-day users.

Be that as it may, even simply having a basic idea about Owner, Group, and Other permissions, as well as the Read, Write, and Execute file access modes can prove to be of value in certain situations.

There are tons of good online resources, but if you're a GNOME user (in particular) and you like a more interactive approach to understanding all of the above, you could try Concessio.

Concessio is a minimalist, free, and open-source application built specifically for the GNOME desktop environment that can do just that - help you understand file permissions.

Before anything else, it's worth noting that the app has a built-in help dialog/menu that explains everything there is to know about UNIX permissions.

Other than that, the app provides a convenient way to convert between symbolic and numeric representations of UNIX file permissions. You can use the toggle buttons to update the symbolic and numeric fields to your liking, and you can even load any file to read its permissions (and convert them).

I have to say, I really enjoyed this app, and I kind of wish GNOME would have such an app by default so that users can understand file permissions better without having to resort to the Internet.

It's true that this is a very simple app and, granted, it could do with a bit more in terms of functionality. One of the improvements for the future (according to the app's GitHub repo) is the ability to update a file's permissions. I would have loved to see this, but I can't really fault the app for this, as it works just as intended.