Hi Brian,
When you open up 'Hidden SSID' a window opens up which asks for:
'Enter SSID, press Next when done'
then
'Enter Password, press Next when done'
Then the BB1 attempts to connect to that SSID.
So it is just provides a way of manually connecting to a network when you know the SSID and the password. The B2 has an identical function, but it is called 'Hidden WiFi'.
Regards,
Peter.