A bookmark, identity or folder has been edited simultaneously on multiple devices or has been deleted. While synchronizing a collision of the different informations occured.
There are different options to resolve the collision:
"delete item locally" = The local item will be deleted
"do not delete item locally" = The local item will not be deleted
"add item" = The local item will be added to the synchronized items
"move to local item" = The cloud item will be added to the local items
"use local item" = The cloud item will be discarded and replaced by the local item
"use remote item" = The local item will be discarded and replaced by the cloud item