Let us first try to understand the term navigation. Simply put, navigation allows a user to move through different pages of content within an application. Windows Phone applications are based on a page model, which is similar to that of Silverlight. Because of this, the navigation in Windows Phone applications is nothing but the presentation of different screens or different contents to the end user thereby allowing him to move back and forth between the content.
Since the Windows Phone hardware mandates a hardware back button, it can be used to go back one screen in any application. There is no need to provide an explicit navigation action to go back in Windows Phone applications.
This type of infrastructure allows the developers to achieve the following:
Creation of different view-based or different screen-based content applications that fit naturally with that of the Windows Phone navigation model
Easy to provide transition when navigating from one view to another...