A Data Dictionary is a centralized repository that contains definitions and descriptions of data elements within a database or information system. It provides essential information about data types, formats, and relationships, helping users understand how to interpret and use the data effectively. By documenting details such as field names, data types, and constraints, a data dictionary serves as a reference for developers, analysts, and other stakeholders. This ensures consistency and clarity in data management, making it easier to maintain and update databases over time.