A secondary navigation menu helps users move through pages below the website’s top-level navigation. It also shows where they are within deeper sections. section 5.1.1
A deeper website section
A top menu may lead to a second-level landing page, which opens further pages three or four levels deep. A sidebar can provide links to those deeper sections while showing the path back to higher levels. section 5.1.1
Figure 5.4 The navigation on this website extends deeper, beyond what’s available in the header navigation. The sidebar on the right serves as navigation to the site’s deeper levels and as a wayfinding tool to let the user know where they clicked from.
See how a sidebar extends header navigation and helps users understand where they arrived from. section 5.1.1
