Do you mean the "syslog daemon" referred to in the main user guide? The "syslog daemon" is used by Brocade vTM to write logging information and alerts to another system. "Syslog" is a standard part of an underlying OS.
However, Brocade vTM software (formerly known as "Stingray") may use one or more other "daemons" as part of its own overall system management. In general, software will use daemons to run background processes or to manage confgurations and resources. For example, a cluster could use one or more daemons to momitor cluster health, and manage transfer of control if a node hits a problem. Similarly, the software might use a daemon to listen in on a management port to accept incoming system commands.