Great user interface design is about communicating information efficiently & effectively. It’s about tearing down the obstacles that get in the way. Sometimes this even means answering user questions before they’re asked, like how google guesses your question as you type.
Navigation is one the most fundamental elements of any application. It gives structure to help the user understand what elements go together. Navigation also dictates process, showing the user what steps go before, what steps they have access to, and unlocking options only after certain steps. Navigation gives the designer control of the user experience through information architecture.
Where real improvement can be achieved by making major changes, the interface designer must balance the legitimate use of familiar paradigms, which ease the learning process, against the enhanced usability that can be attained by abandoning them.