The navigation options in a SharePoint publishing site allow you to manage both the top navigation and the site’s Quick Launch navigation on one page.
SharePoint enables you to manage the two major kinds of navigation found on most websites:
Primary navigation is what your site visitors use to reach the main areas in your site, no matter where they are in your site. Primary navigation is usually positioned somewhere in the top of the page and is consistent across every page in your site. SharePoint calls this global navigation.
Contextual navigation is usually found in the body of the page, usually on the left, and provides access to pages within each major area of your site. This navigation is considered contextual because the navigation items may change, depending on where the visitor is in the site. SharePoint calls this current navigation.
SharePoint provides two navigation menus that correspond with global and current navigation. The Top Link bar is the global navigation menu that’s usually present at the top of publishing pages. The Quick Launch menu provides the current navigation that appears along the left side of most pages.
SharePoint’s publishing site assumes that you want global and current navigation menus created dynamically based on site hierarchy. To that end, configuring navigation in a publishing site requires two things:
A site hierarchy that matches your navigation requirements. In other words, you have subsites for the major items in your global navigation and pages for the items below. Any time you want to create a new grouping of pages in the navigation menu, you have to create a new subsite.
This often leads to extensive nesting of sites, which I recommend you avoid. This is one reason that people start looking for alternative approaches to navigation.
The ability to think in terms of the current site you’re setting navigation options for, its parent site, its sibling sites, and any children sites that may exist. This can be extremely confusing to people, which is one reason many people abandon dynamic navigation. It’s too hard to keep track of what’s happening where.