If this setting is enabled then the specified container will be used as the default root search location for any queries. The container path should be specified in the form of a distinguished name (for example: OU=Users,OU=UK,DC=cjwdev,DC=local). This setting only controls the default, it does not prevent the user from selecting another container when they actually run a query.
If this setting is disabled or not configured then the settings that the user has configured in the Options window will take effect.