DAX, or Data Analysis Expressions, is a formula language used in various Microsoft products, including Power BI, Excel, and SQL Server Analysis Services. It is designed to perform data modeling and analysis, allowing users to create custom calculations and aggregations on their data. DAX is particularly useful for creating measures and calculated columns that enhance data insights. DAX functions similarly to Excel formulas but is optimized for working with large datasets and complex data models. It includes a wide range of functions, such as SUM, AVERAGE, and FILTER, enabling users to manipulate and analyze data efficiently. Understanding DAX can significantly improve data reporting and visualization capabilities.