n - No external messages
Only people in the room can speak to the room. Without +n any user can send a msg to the room and it will be seen in the room.
Privilege: Channel Operator
Examples:
/mode #webchat +n
N - Event Moderation (Recieve From):
This command is set to a room that is receiving moderated messages from a +mM channel, it is a good way of scanning questions when you have a special event. To use both +M and +N modes you must be an network operator and you must be a room op in both rooms. The channel must be +m (moderated) for the messages to go to the receiving channel. See also CMODE M
Privilege: Server Operator
Examples:
/mode #questions +N #event