You interact with iPhone using your fingers to tap, double-tap, swipe, and pinch objects on the touchscreen. To go to the Home screen, press the Home button
.
Open an app: Tap it.

To return to the Home screen, press the Home button
again.
See another Home screen: Swipe left or right.

Go to the first Home screen: Press the Home button
.
View recently used apps: Double-click the Home button
to reveal the multitasking bar.
Tap an app to use it again. Swipe left to see more apps.

If you have a lot of apps, you might want to use Spotlight to locate and open them. See Searching.