At the object level, this is useful for rigging one side of a character and then duplicating the bones to the other side. As you duplicate, you can automatically rename nodes, for example
r_arm is mirrored as
The Mirror Capture tool on the Character shelf tab lets you mirror copy capture attributes (attributes specifying which bones control which parts of the character’s skin) from one side of a character’s skin to the other. See capturing character geometry for more information.
You can add a Mirror node to the network and set its display flag, then edit upstream nodes and see the changes reflected in the mirrored geometry.
If the duplicated geometry has point attributes, the Mirror node mirrors them as well.