FFSync is for updating the database in background (batch). So changes by explorer (copy etc.) are put into the database.
The following actions are executed:

  1. Delete all entries from database without existing files
  2. Add new files to the database
  3. Change database entries for changed files

Without calling parameters deletion is done for all watched directories while add and change is only done for the first watched directory.
A calling parameter other than debug is interpreted as directory (should be a watched directory). If the directoryname contains blanks, include the name with ".
With debug extended output is stored in C:\ProgramData\CF Computer\FastFinder\FFSyncLog.txt.