A staple in BI interview questions, be prepared to answer this one.   This major feature was introduced in July 2018 called Composite Model. Here, Power BI desktop author is empowered to combine the data, which is coming from a variety of sources, and establish relationships between those tables in data model. DirectQuery, which is a large table in SQL server and doesn't need to download in data model. Dual, which is a small table in SQL server, can be downloaded easily into data model. However, this will be only in RAM and will not be saved in .PBIX. To enable this feature, right clicking on the table in the Fields pane and select table properties, another window Field properties pane will appear and can change Storage Mode from DirectQuery to Dual Import, will import the data from sources like CSV or Excel or Azure SQL server or Azure Data Lake or Azure Cosmos to data model and will occupy the space in .PBIX