Data redundancy occurs when the same piece of data exists in multiple places within a database or across different systems. For example, if customer information is stored in multiple databases or tables, any changes made to that information in one location might not be reflected in others. This can lead to data anomalies, where the same data is out of sync, resulting in confusion and errors in data retrieval and reporting. Redundancy can be intentional, for instance, for backup purposes, but often it is unintentional and should be managed carefully.