header-nav layout (/clients/base/layouts/header-nav) is the replacement of header layout (/clients/base/layouts/header) from previous releases.
It hosts four basic view components that compose Sugar's top header, outlined in the image below:
- header-nav-logos
 - quicksearch
 - notifications
 - profileactions
 

Components Impact Overview
| View | Description | 
| header-nav-logos | This new view displays customer logos based on system settings and respects dark/light themes as configured by the user. | 
| quicksearch | 
 It has gone through significant changes, if you customized in any way this component, you will need to refactor your code.  | 
| notifications | No changes | 
| profileactions | Handlebar has slightly changed, make sure to merge with your code for full compatibility | 
You understand the new header-nav, let's get to sidebar-nav:
Move on to Sidebar Nav (sidebar-nav).