It can be important to get a complete Snapshot of the main configuration and usage within your Office 365 Tenant. With that in mind there is the Inventory Report under the tenants node.
This report is very lengthy and combines a lot of information into a single report. This can be very helpful when doing more high level reviews or planning. Information is based on data collection across all services and workloads.
The reports put logical information into natural groupings for easy access of pertinent information.
There is also a section with high level traffic and usage groupings.
As with all of the reports, this information can be customized, filtered and scheduled.