What is a View Reference in Revit?

The term 'View Reference' refers to a automatically updating link symbol that can be added to a Primary or Dependent View if the Primary-Dependent Floor Plan situation exists.  That is pretty much its only purpose.  Here is some more info from Wikihelp:

A view reference is a symbol. You can create a view reference family in the Family Editor. View reference families can contain lines, filled regions, text and labels for the view number and sheet number parameter values.

View references display in the primary view and all related dependent views (except for the view that it is referencing). For example, if you have a view split into 2 dependent views (left and right), and you add a view reference to the right view to reference the left, the view reference appears in the primary view and in the right view, but not in the left view.

Info via
Navigating Primary and Dependent Views - WikiHelp

 

Also check out:
View References (excerpt below)
 Now what would be REALLY useful (to anyone trying to read our drawing set) would be a reference near the matchline to tell you what sheet to find the other part of the plan. This is where "View References" come into play....