…and the answer is not necessarily in the users home directory.

Imagine you write a desktop app and you need to persist some configuration the user has chosen. Where do you put those files? My default answer – as I have been a developer on a Mac – would have been ~/Library/Application Support/com.example.AwesomeApp/. But since I am working with Linux now, and those people have different ideas where to put stuff and like to have total control, I would have said something like: “In a dotfile maybe?”

But there seems to be a specification for handling this – of course, there is. So the short answer is, if there is the environment variable $XDG_CONFIG_HOME defined, use that value, if not, default to ~/.config for config files. And for other app-specific files use $XDG_DATA_HOME or ~/.local/share

So if you build a desktop app, you know now, where to put stuff.