Here, you can reboot the firewall or restart certain modules.
When the firewall is rebooted, all active SIP sessions (SIP calls, video conferences etc) will be torn down. SIP user registrations are not affected.
When the SIP module is restarted, all active SIP sessions (SIP calls, video conferences etc) will be torn down and all SIP user registrations will be removed.
N.B! The reboot/restart will be instantaneous when the button is pressed.

When this button is pressed, the firewall will immediately reboot.
All active SIP sessions will be torn down at the reboot.
When this button is pressed, the SIP module of the firewall will restart and all SIP registrations will be removed.
All active SIP sessions will be torn down and all SIP registrations will be removed at the restart.