As you create text-only topics for What's This? Help, RoboHELP writes information about them to text-only topics files (.TXT). This file shows the topic ID and its matching text. This is the text that is displayed as What's This? Help.
The .TXT file is included in the HTML Help file (.CHM) when it's compiled.
When users request help, the HTML Help engine looks up the field/control they want help about in a mapping table and identifies its map number.
It looks up the map number in the map file and translates it into its matching topic ID.
It looks up the topic ID in the .TXT file and displays the topic in the application.
Your HTML Help project can include one or several .TXT files, depending on how many map files you want to work with. Each .TXT file and its corresponding map file use the same names (for example, Pizza.h and Pizza.txt).