A navigation bar:
Is translucent
Generally appears at the top of an app screen, just below the status bar
In a horizontally regular environment, a navigation bar can also display within a view that doesn’t extend across the screen, such as one pane of a split view controller.
Can hide when the keyboard appears, the user makes a gesture, or when the containing view controller transitions to a vertically compact environment.
Can be tinted. (Use tintColor to tint bar button items; use barTintColor to tint the bar background.)