The background service synchronises without the program window having to be open – even when nobody is logged in. It uses the same configuration file as the program, that is the same synchronisations with the same options.
The Background service menu holds Start and Stop. Under View → Background you can see whether the service is running at the moment.
The installation package lets the user the service runs as start and stop it without an administrator password. Other users are asked for an administrator's password.
Service and program stay out of each other's way: only one of the two synchronises at a time, so that two runs never touch the same files at once. If you choose Start in the program while the service is working, the service steps back.
The service reads the configuration file. Since the program saves every change at once, a running service takes it over by itself: it aborts the run in progress and starts over with the new configuration. Only if saving failed does the window title show (unsaved), and the service keeps working with the old state; when the service is started, the program then asks whether to save – Cancel does not start the service.