The core of this is often overlooked or missunderstood. Let me boil it down.
The limitation of screen size combined with the immediatacy of needing to
do something else contribute to the need to lower cognitive loads.
In plain English, help the mobile user get the information with less
thinking because you have a smaller screens and limited resources on a
mobile device. What does this mean?
Navigation, menu items are no longer lists of sections in an area.
you should be using less menu items. That also means you should be using
those visual and other cues that indicate possible actions in a
section of your application with a cohesive set of common actions
that mean the same across all areas of your application.
Another way to rememebr is you see the phrase, give the user the
real object to manipulate. In the case of most mobile applications that real object
happens ot be content within the application.Balance input loads. On desktop the action of clicking a menu or scrolling a page was small as the mouse input system takes a tiny small movement of the
hand and translates that to a large movement on the desktop screen.
Because of the screen space limitations you have no similar input translation on moible and thus
you want to reduce extra user touch movements whenever possible. If you can reduce
7 clicks to do something to 2 than you should strive to do that optimization.
Do not be afraid of experimentation. In the Web application world there is an web application that defies UX conventions, its not pretty visually. It looks like something from the 1990s web in fact. What is hidden is the behind-the-scense appliction of modern html5/css3 to deliver something that works well both in web application form and mobile application form. The web application I am referringto is in fact Craigslist.org.
Craigslist team used the organization of links within their menu system to reduce cognitive loads and eliminate the use of the dreaded dropdown which freed them up to have a UI that is future proffed no matter what new internet tecnlogy comes down the rod as far device form factor, etc.