The Type hierarchy view allows to explore the type hierarchy of a schema type. If you select a schema element in another view, e.g. the Schema Explorer, the hierarchy of the associated type, with its super types and sub types, is displayed in the Type hierarchy view.
The type for which the hierarchy is displayed is marked with a violet background. When the Type hierarchy view is active, you can focus on another type in the hierarchy by double-clicking on it, switching to this type's hierarchy.