The Class and Calls view helps you understand source code's control and data flows, together with their class context. You're able to see which functions (blue) call or are overridden by other functions, and where variable (green) accesses and assignments occur. You can see how the functions and variables relate to the class (orchid) structure.
One application the Class and Calls view is to examine the use of class members by other classes. For example, a simple query will show which classes indirectly set a specific variable, through the calls and overrides of their member functions. 