What do these icons mean?

Settings > Preferences > Favorites and Recent > Folder Aliases
Little blue chain thingies
What are they?


Presumably they appear for the same folders in File Explorer as well?

Yes they appear in listers as well.
And it turns out in windows explorer.
AND I know what they are.
From within Microsoft Teams you can share files to onedrive native if you like.
If you do that the folder appears in your Onedrive folder with the funny icon.