What is the Power BI Report Server (and how does it differ from the Power BI Service)?
The Power BI Report Server is the on-premise equivalent of the cloud-based Power BI Service combined with a Microsoft SQL Reporting Services server. It includes tools to publish Power BI paginated and other reports accessible via a web browser or mobile device. The Power BI Report Server can also be thought of as the next generation Reporting Services (SSRS) product.
Licencing of the Power BI Report Service is either via Power BI Premium or a SQL Service Enterprise Edition licence with Software Assurance.