This command is used to invite yourself into a room that is set to invite only. You need to have User (UOP) or higher access in the target room to utilize this command. This command cannot be used to invite others into the room.
Example:
/msg chanserv invite #conferenceroom
This command is useful if the room is set +i, because without inviting yourself, you cannot join. To invite others, use the command /invite <nick> <room> while opped in the room. Invite-only rooms allow for some privacy, since people cannot join without the approval of the ops.