Attendant settings define where calls are forwarded when a caller presses 0 while listening to your voice message greeting.
The options available for Attendant are:
Default attendant (operator): Calls are routed to the system attendant (operator).
Personal attendant/assistant: Calls are routed to another phone number. You must enter the phone number, which can be internal (typically a phone extension) or external (any phone number formatting is acceptable).