Config in wx examples

Dear Erlangers,
In this module from the manual;

 -module(ex_notebook).

		-include_lib("wx/include/wx.hrl").

		-behaviour(wx_object).

		-export([start/1, init/1, terminate/2, code_change/3,

		 handle_info/2, handle_call/3, handle_cast/2, handle_event/2]).

		-record(state, 

		 {

		 parent,

		 config,

		 notebook

		 }).

		start(Config) ->

wx_object:start_link(?MODULE, Config, [])......

Apart from the argument being a variable and a data field in the state
record, in this context what is Config ?

Thank you in advance.
Peter