Description: &If a resource supports instances, this must be the name of an instance for which to add or remove a watcher. The instance name is the third index used by the agent in the different MIB tables for this resource. If a resource does not support instances, should be used as third index. If used as a filter element for auto discovery, this name can be a regular expression (case-insensitive). In this case, it restricts the resources to be searched for during an auto discovery run.