A conflict occurs when the same document is modified on 2 or more devices simultaneously. This can happen if you change a document on your iPhone when there is no internet, then return to the office and update the same document on your Mac BEFORE it has had a chance to pull down those changes you made on the iPhone. Question is - which document is the one to carry forward?
See below for what happens when a map has been modified on both iPad and Mac.
Ideally the system would simply merge the changes. However, this is difficult to do reliably - so iThoughts requires you 'pick one'. To assist with this decision, the device on which the map was modified, the modified date and a thumbnail image are presented.
Once you've picked which map to take forward, the other devices will be informed and reload themselves automatically (i.e. no need to pick the map on each device.)
On iOS you have the option to 'Keep All'. This will choose the first map in the list to carry forward, but also save local copies of any other versions - enabling you to manually merge any changes.
On OS X you can use the 'version history' feature to recover changes from previous versions of the map.