The g:gtype structure represents the unique identifier of a registered foreign GType type on the Lisp side. In the C library a GType type is represented as an integer. The g:type-t type specifier automatically converts between the Lisp g:gtype representation and the C integer. Create a g:gtype instance from a GType name:

(g:gtype "GApplication")
=> #<GTYPE :name "GApplication" :id 94607290994400>
(g:gtype-name *) => "GApplication"
(g:gtype-id **) => 94607290994400