Users often search through the index of a printed book to find the page containing the information they're looking for. In a similar way, your index allows users to search for information too, but much more interactively. In fact, studies show that the index is used more frequently to find information than the table of contents or full-text search. An index allows users to quickly get to the information they need and want.
The Help index displays a multilevel list of topics and keywords or phrases that you create. There are two ways users get to topics using the index:
Typing. Users can type a keyword or phrase and go directly to a topic or to a list of topics containing that keyword or phrase.
Browsing. Users can also browse through the index, then select a keyword or phrase. They either go directly to the topic or to a list of topics containing the selected keyword or phrase.
You can have as many keywords and phrases as you want or need. When creating an index, don't just limit yourself to terms inside the Help system. It's a good idea to cross-reference keywords with synonyms. Carefully consider the words or phrases according to your users' ways of thinking.