Navigation in SharePoint is generally considered the menu elements (top navigation bar, quick launch, bread crumbs, etc) and the links contained therein. Navigation is one aspect of Informaiton Architecture.

Navigation schemes should make it easy for users to find desired information. On a website, the information architecture can also add important context to the current page (i.e. the location of the page in context with the entire site)

Types of Questions:

Custom Navigation items (Menu, quicklaunch, links, etc)
Menu configuration(s)
Information Architecture regarding Navigation
Navigation schemes
Design realted questions