M-Query is a formula language used by Microsoft Power Query to connect, filter, combine, and transform data from one or more supported data sources. It provides the logic behind repeatable data preparation processes and is used across Microsoft products including Power BI, Excel, Analysis Services, Dataverse, and Fabric.
As a functional and case-sensitive language, M enables users to build data transformations using expressions, functions, operators, variables, and conditional logic. It is especially valuable for shaping and preparing data before analysis, helping organizations turn information from different sources into consistent, structured datasets that can support analytics and reporting.