A relational database optimized for analytical queries over structured, modeled historical data, usually in a star schema. It applies the schema when writing data (schema-on-write).
In DP-900 it is compared with the data lake (raw files) and the lakehouse (combines both). In Microsoft Fabric, the Fabric Data Warehouse offers full T-SQL with transactions over Delta data in OneLake.
Data warehouse is a concept that can show up on the exam. Check the full guide to see it in context.