Power BI Desktop makes discovering data easy. You can import data from a variety of data sources. After you connect to a data source, you can structure the data to meet your analysis and reporting needs. 

Create relationships and enrich your data model with new measures and data formats. 

When you import two or more tables, you often need to create relationships between the tables. Power BI Desktop includes the "Manage Relationships" dialog box and the "Relationships" view, where you can use auto-discovery to have Power BI Desktop find and create any relationships or create them yourself. You can also create your own measures and calculations very easily, or customize data formats and categories to enrich your data to gain additional insights.

Power BI Desktop includes the report view. Select the fields you want, add filters, choose from dozens of visualizations, format your reports with custom colors, gradients, and various other options. Report View gives you the same great report creation and visualization tools used to create reports on PowerBI.com. 

Power BI Desktop allows you to save your work as a Power BI Desktop file. Power BI Desktop files have the file extension PBIX.

You can upload the reports you have created and saved in Desktop to your Power BI website. Furthermore, you can also publish them to Power BI directly from Power BI Desktop.