In GDScript, functions are not [i]first-class objects[/i]. This means it is impossible to store them directly as variables, return them from another function, or pass them as arguments.
However, by creating a [code]FuncRef[/code] using the [method @GDScript.funcref] function, a reference to a function in a given object can be created, passed around and called.
The object containing the referenced function. This object must be of a type actually inheriting from [Object], not a built-in type such as [int], [Vector2] or [Dictionary].