"Photos synced from Finder will be removed"
For a while, my phone was not syncing with iCloud. Now when I go to iOS prefs and turn it on, it warns me that "Photos Synced from Finder will be Removed". Syncing photos via Finder is not supported with iCloud Photos is turned on. 177 photos will be removed."
Obviously, I would like not to lose 177 photos. What does this warning refer to? What exactly is "syncing from Finder"? and what photos am I likely to lose?
iPhone XS