In some organizations, configuration management is the term given to the identification, tracking, and management of all the physical assets of a project. In other organizations, configuration management refers more narrowly to the description and characteristics of the assets. In either case, on large projects you might be interested in tracking certain important items in the project. We'll call these items "configuration elements" and the definition of these elements may be defined by your company.
A full configuration management process requires planning, tracking, managing, and reporting your configuration elements. Periodically, or at major milestones, you also need to validate that your tracking processes are working correctly. This last essential element of the configuration management process is auditing.
Configuration management starts with a baseline description of your configuration elements. If these elements never changed, there would be nothing else required. However, generally your configuration elements are susceptible to change during the project. You want to make sure that your tracking process is sufficient to account for any changes from the baseline.
Auditing, then, involves validating that the actual configuration elements (whatever they are) at any given time are the same as what you expect. Many projects get in trouble when they start to lose track of physical assets (for instance, material, supplies, code) or if the physical characteristics (metadata) of your deliverables is different than what you expect.
The auditing process is used to validate that the configuration elements match up with your expectations. These expectations are based on the original baseline, plus any change requests that you have processed up to the current time. For physical assets this would mean that your inventory reports match a count of the actual physical assets at the current time. If your configuration elements involve descriptions and other metadata, you would be validating that the descriptions and characteristics are consistent with the way the deliverables are actually being built.
If the audits don't result in the expected results, it would mean that your configuration tracking process is inadequate and that you should improve your processes to account for all changes. You would need to identify the ways that your configuration can change over time, and validate that you are catching all of these instances in your configuration tracking process.
Configuration audits are difficult and expensive in terms of resources and time. Nevertheless, they are vital in ensuring that the final solution is complete and correct and that you have accounted for all of the configuration assets used to build the final solution.