A semantic layer is a translation layer between raw data and users (both human and machine), provides a unified, meaningful, and user-friendly view of complex and often distributed raw data, enabling consistent understanding, easier access, and better governance of data across tools and teams. The semantic layer - Defines business-friendly terms and concepts (e.g., "Customer", "Revenue", "Order Date") rather than raw column names like `cust_id` or `txn_dt`. - Maps these concepts to the underlying data structures across tables, files, or systems in your data. The semantic layer often includes [[metadata]], relationships, rules, and [[ontology|ontologies]] to add meaning and context.