How to Switch between Open Apps (More ways in iOS 5 & 6)

When running an app, you can minimize it by simply clicking the Home button. Getting back to it is not just one click on the taskbar like the way you do in Windows. But the iPad way is not difficult either.

On the iOS 4, 5 & 6

Double-click your iPad's Home button to reveal the open apps on the multitasking bar at the bottom of the screen.
Flick left to see more running apps.
Tap an icon to instantly switch to an open app.

On the iOS 5 & 6 only

You can use four or five fingers to swipe left or right to switch between open apps, or swipe up to reveal the open apps on the multitasking bar.