Unified data governance, protection and compliance platform. It discovers and catalogs data across Azure, on-premises environments, other clouds and SaaS applications (Data Map), classifies it automatically (for example personal or financial data), shows its lineage and includes compliance tools such as Compliance Manager. It was formerly called Azure Purview.
In AZ-900 it is in the skills outline as a governance and compliance tool, alongside Azure Policy and resource locks. Key difference: Azure Policy governs resource configuration; Purview governs data. In AZ-305 it comes up when designing data governance: catalog, classification and lineage. Question: discover and classify sensitive data across the organization → Microsoft Purview.
Microsoft Purview is a concept that can show up on the exam. Check the full guide to see it in context.