@torbuntu GLib.Variant is a generic variable type that can represent anything from strings to arrays or unions. They are used mostly when interacting with the bindings or other services (like actions). You probably don't want to use them unless you plan to pass them to the bindings etc. Vala's post shows how easy it is to cast them to vala-native types, if you are working with them!

Here's an example: https://valadoc.org/gio-2.0/GLib.SimpleAction.change_state.html
That signal's value can be anything, you have to cast that Variant to the vala-native type it represents to use it