The aim of a website's navigation is simply to allow users to get to the content they require. For sites that have a large number of sections and web pages (and information sites can be one of these) the navigation plan has to be properly researched and designed.
A usable site will: Help users achieve a goal, usually to find something, such as information, or obtain something, such as an article; Make it easy for them to achieve that goal; Make it possible to achieve the goal quickly; Make achieving that goal a pleasant experience.