You start browsing a class hierarchy parsed by ebrowse by just finding the BROWSE file with C-x C-f.
An example of a tree buffer display is shown below.
| Collection | IndexedCollection | Array | FixedArray | Set | Dictionary
When you run Emacs on a display which supports colors and the mouse, you will notice that certain areas in the tree buffer are highlighted when you move the mouse over them. This highlight marks mouse-sensitive regions in the buffer. Please notice the help strings in the echo area when the mouse moves over a sensitive region.
A click with Mouse-3 on a mouse-sensitive region opens a context menu. In addition to this, each buffer also has a buffer-specific menu that is opened with a click with Mouse-3 somewhere in the buffer where no highlight is displayed.