Dynamic Reference Visualization, is a new feature in SolidWorks 2015.
Dynamic Reference Visualization lets us view the parent relationships between items in the FeatureManager design tree. When we hover over a feature with references in the FeatureManager design tree, arrows display showing the relationships as shown below.
If a reference cannot be shown because a feature is not expanded, the arrow points to the feature that contains the reference and the actual reference appears in a text box to the right of the arrow as shown below.
To turn on Dynamic Reference Visualization, in the FeatureManager design tree, right-click the first item (part or assembly) and click Tree Display > Show Dynamic Reference Visualization as shown below.