Class hierarchy
'Class hierarchy' view allows to browse class hierarchy, that is to see for a class its superclass chain, as well as classes which extend the class.
'Class hierarchy' is a slave view. The hierarchy is shown for the class selected in the master table (e.g. in Class list) or for the class of objects selected in the master table (e.g. in Objects explorer).
Use IDE integration to open class in your IDE, should you need to use more powerful hierarchy analysis capabilities provided by your IDE.