A Configuration Item is any service component, infrastructure element, or other items that need to be managed in order to ensure the successful delivery of services. Examples of CI include individual requirements documents, software, models, and plans.
Configuration Management is the practice of handling changes systematically so that a system maintains its integrity over time. Configuration Management (CM) ensures that the current design and build state of the system is known, good & trusted; and doesn’t rely on the tacit knowledge of the development team.