Workers can be configured locally on each system or centrally from the Supervisor.
A Supervisor autodiscovery process is used by Qube! as a means to quickly identify the Supervisor without any local configuration necessary. If the Supervisor isn't explicitly set in the Worker's configuration file, it will use autodiscovery to find the Supervisor host name and IP address. However that Supervisor and Worker must be on the same network subnet. Once it has that information it can then gather configuration from the Supervisor and continue the startup configuration process.
In general, it is preferable to explicitly name the Supervisor however, since this speeds job startup time and reduces network traffic slightly.