Defines the name and location of an ASCII text file that contains a list of items. Depending on the circumstances, the file can include mapped topic IDs. Including an ASCII text file provides an alternative to adding these items individually. If you do not know the name or location of the file you want to include, click the [...] button.
The HelpIncludeFile element corresponds to the "Instead of context mapping use this Include file (*.hm)" field on the Linking sub tab, on the Windows Help tab of the Book object.