With the arrival of iOS 6, users have begun using the new turn-by-turn directions built into Apple's mapping app. iPhone 5, 4S and iPad 2 and 3 users get turn-by-turn navigation with spoken directions that automatically route users to their destination. The iPhone 4 does not support the much promoted feature.
In iOS 5's Google version of Maps, the app provided directions in list-form and allowed users to press 'next' and 'previous' to navigate from turn to turn. Though the iPhone 4 doesn't officially support turn-by-turn directions, Apple has significantly upgraded how the Maps app presents them.
Directions are displayed on the screen in the same style as "turn-by-turn" but users can swipe manually just like the iOS 5 version, or the directions change after you reach the turn.
Article Link: How the iPhone 4 Displays Map Directions in iOS 6