Customization is the effort which is involved to significantly modify the inherent utility of a product or service to fit a specific need using highly trained resources to accomplish a specific purpose. Customizations are typically more expensive than simple configurations given the highly talented labor pool that is required to execute. A very good heuristic to use when determining if something is a configuration or a customization, is to think of someone that you know well outside the field of endeavor that you are in, then postulate a situation, where you wanted something changed in a technology that you use frequently. If this individual could accomplish your request with minimal guidance, then most likely you requested a configuration. If the request that you made cannot be satisfied with ease or without several additional questions, then most likely you have requested a customization for which this individual does not possess the necessary skills to accomplish.