What is the difference between Back-Up and Sync in Onedrive?

Hi, janreinecke

Thank you for the recognition. Perhaps you can mark a yes for my response, much appreciated!

Regarding the difference between backup and synchronization in OneDrive

Backup and Sync have different purposes in OneDrive:

Backup: The automatic backup function of OneDrive will automatically back up local user folders on your computer (such as desktop folders, picture folders, document folders, etc.) to OneDrive. When you turn on this function, changes you make to the backup folder will be automatically synchronized to OneDrive.

Sync: The manual upload synchronization function of OneDrive means that you can manually drag files and folders into the OneDrive folder, or upload them to OneDrive on the OneDrive webpage. When you make changes to files that have been uploaded to OneDrive, the OneDrive webpage, OneDrive mobile, and OneDrive desktop applications will synchronize the changes.

These two features work in a very similar way, you can refer to this thread: Is there any difference between OneDrive BACKUP and OneDrive SYNC - Microsoft Community

Detailed guide to OneDrive settings

For a detailed guide to all the settings available in OneDrive, you can refer to the official Microsoft Support page. This page covers everything from managing storage, synchronizing files, setting up backups, and more:

How to access OneDrive settings - Microsoft Support

Best wishes

Aiden.C - MSFT |Microsoft Community Support Specialist