The publish step sends the report from the Power BI Desktop to the Power BI Service (cloud).

See the Microsoft documentation: Create reports in Power BI . You need a report to begin.

To publish a report to Power BI Service (cloud):

  1. Select Publish from the Power BI Desktop report dialog.
Microsoft Power BI report dialog with a left menu that displays the Publish option.

The publishes to the Power BI Service (cloud). Sign in to Power BI Service to see the report.