DirectQuery: No data is imported or copied into Power BI Desktop.
Import: The selected tables and columns are imported into Power BI Desktop. As you create or interact with a visualization, Power BI Desktop uses the imported data.
Benefits of using DirectQuery
There are a few benefits to using DirectQuery:
* DirectQuery lets you build visualizations over very large datasets, where it would otherwise be unfeasible to first import all the data with pre-aggregation.
* Underlying data changes can require a refresh of data. For some reports, the need to display current data can require large data transfers, making reimporting data unfeasible. By contrast, DirectQuery reports always use current data.
The 1-GB dataset limitation doesn't apply to DirectQuery.
Reference:
https://docs.microsoft.com/en-us/power-bi/connect-data/desktop-use-directquery