Category Map works when you are receiving audio from another PlayoutONE System via the PlayoutONE Synchroniser.
You may need to use Category Mapping when the station sending you the audio is part of a Multi Station. By default Auto Importer imports the category from 'Station1' however you may wish to import category information from Station 2, 3 or 4.
To alter the category mappings, tick 'Use Synchroniser Category Mappings' and then alter the Category / Alt Category Import Station to match the Multi Station number of the sending station. The sending station can find their Multi Station number when opening the Station Settings within PlayoutONE Monitor as shown below.