What are default databases which gets installed with SSRS during its installation?

SSRS by default install two databases in SQL SERVER. These databases contain the configuration parameter to support the report server and report manager. It also stored the execution and processing time of each and every report rendered via report server.

Report Server: This database stores the items like linked reports, shared data sources, folder structure. It also stores the report models, subscriptions, schedule and log data.

ReportServerTempDB : Temp DB as name suggested it stores the temporary information related to report execution. It stores information like session information, execution data, cached report