Help project files for Microsoft HTML Help projects have the .HHP file extension. HTML Help projects also contain many more files than WinHelp projects, since each Help topic is a separate file.
RoboHELP allows you to create custom folders for your HTML Help projects to organize project files and make it possible for several Help authors to work together on modular Help systems and multiple projects. Custom folders reside on your system and support relative paths - paths from the project folder to files in your custom folders.