Soheil Bakhshi summarizes the set of reporting options available in Power BI:
Power BI Service
Power BI Service is a SaaS (Software as a Service) offering from Microsoft in the cloud. The users within an organisation, depending on their access rights, may create reports directly in Power BI Service. The users can also securely share and distribute those reports. While creating or editing reports is possible in Power BI Service, it is strongly recommended to avoid this method for several reasons. The most obvious one is that the changes we make to a report may soon get overwritten by someone else that republishes the same report from Power BI Desktop. Check this blog post from SQLChick to see why you should avoid creating or editing reports directly from Power BI Service. The reports are downloadable in PBIX format.
Click through for the full list and lots of detail.