A Help system is actually the result of a process called Help authoring:
These are the parts that make up a Help system. There are many other features you can add, specific to the Help format and application you're using.
Topics are the basic units of a Help system. They communicate the message, mainly through text and images.
Windows display the topics so users can view them.
Links connect topics so users can navigate from one to another.
Styles determine the layout and appearance of topic text.
The table of contents presents an outline of the contents of the Help system (much like a printed book).
The index contains keywords and phrases enabling users to find information (much like the back of a printed book).
Full-text search provides a way for users to search for particular words or phrases to find topics.
Authors create Help projects in a Help-authoring tool such as RoboHELP or RoboHELP Classic to create the message files and a Help project file. The project file allows you to manage and organize all the topics, images, sound, video, and appearance files that go into the Help system.
When you complete WinHelp or HTML Help projects, you combine all the files into a single Help file by generating them. A Help compiler uses the information in your project to determine what the Help system contains and what it looks like.
A special window known as a Help viewer is used to display the Help system. This viewer resides on your computer. Sometimes Help viewers are called Help engines, because they display (or "run") the Help system. Some Help systems are displayed in browsers that function like a Help viewer when the Help systems are running.