When you Archive your Office 365 groups, the files and folders in the libraries of the Team Site connected to the Office 365 group are put into ShareGate Azure storage (for information on security, click here). You can retrieve them at a later date if needed.
- Files and folders in libraries.
- SharePoint's hierarchy (transformed into folders).
What's not archived:
- SharePoint-related metadata.
- SharePoint permissions.
- Content specific to other workloads (Teams, Outlook, etc.)