In Power BI, an Aggregation Table is a type of table that stores data at different levels of aggregation, such as sum, average, minimum, maximum, and count. This can be useful when you want to analyze data at different levels of detail, or when you want to improve the performance of your Power BI reports by reducing the amount of data that needs to be processed.
To create an Aggregation Table in Power BI, you can use the "Create Aggregation" feature in the Power BI Desktop app. This will allow you to specify the level of aggregation that you want to use, as well as the columns that you want to include in the table. You can then use the Aggregation Table in your Power BI reports, just like any other table.
One thing to keep in mind is that Aggregation Tables are created as part of the Power BI data model, and are not stored as separate tables in the underlying data source. This means that you will need to refresh the data model in Power BI in order to update the Aggregation Table with any changes to the underlying data.