Here is How you close out an iPhone app that is running in the background

Question

How do you close out an iPhone app that is running in the background in the new iOS 4? We’ve had more than one reader ask this question since the launch of the new iPhone operating system, and the iPhone 4, last week. Some have asked about this due to battery drain concerns, and others just because they want to be able to shut down a backgrounded app.
So this seems as good a time as any to share a quick tip on how you can force apps to close in the new iOS 4.
There are two ways to fore an app to close down under iOS 4. The first is by doing a ‘force quit’ on the app, just as we have done under the previous version of the iPhone OS. To do this, you press and hold the power button while you are in the app you want to close down. Wait for the ‘Slide to power off’ bar appears across the top of the iPhone – then don’t hit Cancel, but instead just hold down the Home button continuously until the app closes and you drop back to the home screen.
The much easier method now available in iOS 4 is to use the Multitasking bar to close any app you want. Here’s how:
– Double tap the Home button to bring up the Multitasking bar
– Press and hold anywhere on the multitasking bar until the icons on it start to wiggle.
– While they are wiggling, each icon has a Minus sign symbol above it.
– Press the Minus symbol above any app to close it down.
That’s it. This will work for any app you want to close, including the Apple built-in apps like Mail and Safari etc.
Hope this quick tip is helpful to some of you who are getting to know iOS 4.

Answer 1

The apps on the bottom are recently accessed apps. Instead of closing when you exit the app they go into a suspended state, and will load faster when you next launch them. Unless they are a streaming app (like Pandora) they do not use any power when they appear in the active app list.
This information, as well as the OP's post, are in the latest user guide. I guess nobody reads manuals anymore