In an application there may be many different launching points that open the help system. Each launching point needs to have a unique identification number or be programmed with the URL to the page that should be opened.
If the unique identification number method is used, something called a "Map File" needs to be created. If the simple URL method is used, the Application Developer simply needs to know what that URL is, so that s/he may create the correct link within the application.
Communication between the Help Author and Application Developer is crucial.