The Relationships Browser can optionally display refinement relationships (including inheritance) in a hierarchical tree view. To enable this option, select Show Refined By button on the Browser page of the system settings. (See System settings for more information.)
If you select this option, refining elements show up in the browser as nested children in either the source pane or the destination pane. If an element has children, a plus sign (+) button appears beside the element in the list. Select this button to expand or collapse the list and display the refining elements.
There are several kinds of refining elements: