What's the iPad ALT + TAB?

In Windows you can ALT + TAB on the keyboard to switch between programs, what's the iPad equivalent?

There are several ways to accomplish the same task, for those without a keyboard one of the below will work:

1. Swipe up from the bottom off screen, this will present you with the iOS task bar, select App from there. Swipe all the way up and you'll get the list of current running apps.
2. 4 finger and thumb on the screen in a spider shape and pull all together
3. 4 fingers on screen and swipe right

For those with a keyboard:

1. Hold down the Command button and press Tab