The integration of SSRS and Power BI creates a single portal to access all reporting items; which would be from Power BI dashboard.
For using this functionality, some requirements need to be met. You have to use SQL Server 2016 or higher version. Your dataset of the report should be using saved credentials. SSRS report should have charts, gauges, or maps, because only charts, gauges, and maps can be pinned to the dashboard. Power BI Integration in the reporting services configuration manager should be enabled. And finally; SQL Server agent should be up and running because Agent is responsible for keeping that tile up to date.
Using the integration of SSRS and Power BI; you can have tiles in Power BI dashboard which points to SSRS reports for the detailed paginated report. Power BI users will use normal tiles for interactive reports, and they can use SSRS tiles when they want to see the more detailed paginated report in SSRS.