The four main components of a Power BI Report Server deployment include the report server instance, the Report Server Database, Active Directory, and the data sources used by the reports. The Active Directory domain controller is needed to securely authenticate requests by both the data sources and the report server.

In the following diagram, a SQL Server database and an SSAS Tabular model are used as the data sources by the report server: 

In the diagram, the Report Server Database is hosted on a separate server than the Power BI Report Server. This is recommended to avoid competition for resources (CPU, memory, and network) between the Power BI Report Server and the SQL Server database engine instance required for the Report Server Database. Additional information on the Report Server Database and configuring this remote connection is included in the following sections.