Unison: Liberation through Data Replication

Unison: Liberation through Data Replication: This document describes some of the benefits of using Unison and provides some tips on doing so, although it is not meant to be a comprehensive how-to guide or user manual.
Another discussion on Using Unison can be found here.
However, neither really answer my current question which is "When using the 'backupdir' parameter in batch mode, do the backups exist on the client/source or server/destination?"