ClientConfig is the by product of a workshop at MODXpo Europe 2012, the "Developing Extras in MODX" one. See the session page at modxpo.eu http://modxpo.eu/2012/schedule/sessions/developing-extras-for-modx-hands-on for more information and footage of the workshop.
ClientConfig gives your client an user-friendly interface for making site wide changes, while you as the administrator set up the different options available to the end-user.
Possible uses include: