This view can be opened to gain insight into the HTML and XML source files that are used to contribute to the Eclipse help system. It can be set up to be in sync with the Help Explorer and automatically show the contents of a referenced file on selection of an entry. It can be displayed using the main menu path Window | Show View and following the tree path Eclipse Introspection | Source in the dialog Show View.
The Source view looks as following:
Navigating the help system
Help Exporer view