If you are familiar with other publishing systems, you may be accustomed to formatting information as you like to see it. Authoring with HelpTag requires you to think about structure and content, not format.
As you write, you use tags to mark certain types of information. When you do so, you are identifying what the information is, but not how it should be formatted.
For instance, to refer to a book title, include markup like this:
<book>System Administrator's Reference Guide</book>
This abstraction separates structure and content from format, which allows the same information to be used by other systems and perhaps formatted differently. For instance, Help displays book titles using an italic font. However, on another system an italic font may not be available, so the formatter could decide that book titles are underlined.