Kristyna Hughes shows how to create an info tooltip in Power BI:
The steps below will walk through how to add an information icon to the report, making a tooltip page containing your additional information, and enabling the tooltip to allow users to hover over the icon and see the information.
This can be quite useful, especially as it gets context information out of the way of users after they don’t need it anymore. That’s important for dashboards you expect people to look at regularly.