Basics : many way to use a Procedure

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Hello !

I'm seeing that some people use procedure with the sign " => " .
What is it ? Any documentation about this ? 

A example =

Ada.Text_IO.Create (
          File => Log_File,
          Name => "my_log_file.txt",
          Mode => Ada.Text_IO.Out_File);


which is very similar to the prototype :

 procedure Open
     (File : in out File_Type;
      Mode : File_Mode;
      Name : String;
      Form : String := "");

Also , is it possible to apply this kind of writing  for this procedure ? =

procedure Gtk_New
     (Window   : out Gtk_Window;
      The_Type : Gtk.Enums.Gtk_Window_Type := Gtk.Enums.Window_Toplevel);


Thanks for your answers :)