How do measures differ from calculated columns?

The distinction between measures and calculated columns is fundamental to understanding data modeling in Power BI. Measures are indeed calculations that are performed at query time, meaning they are evaluated based on the context in which they are used when a report is generated or a visual is rendered. This allows them to encapsulate dynamic aggregation, enabling them to react to filters, slicers, and the contextual data surrounding them, providing real-time analysis based on user interactions.

In contrast, calculated columns are computed during the data load process, meaning their values are statically generated when the data model is built. They become part of the table itself and don't change based on report filters or slicers. Instead, their primary role is to add new data to the model that can be used in various ways, but they lack the ability to adjust based on the interactive elements of a report.

This fundamental understanding is crucial for effective data analysis, as it helps in deciding how to best optimize performance and the user experience in Power BI reports.