There is only one button at the bottom of my iPod Touch. To close applications, I press the home button. Does it really close applications, or does it just display the home page and an extra thread runs in the background? Is there any way that I can see the currently running applications?
In iOS 3, you press the home button, with very few and only Apple-engineered exceptions (eg. the iPod app) the app is closed.
In iOS 4+, there is limited multitasking available to third-party apps. Apple freezes all processes in the background unless they're performing one of the following functions (ripped from Ars):
In iOS 4, double-tapping the home button shows a tray holding both recently-used apps and apps performing the above limited-multitasking functions. You can close them/remove them from the tray by clicking the red "-" sign.
If you use iOS 4 (or higher) tapping the Home button to close an app now only hides the app's activity and don't closed really, if you want close app you must "double tap button hold the icon then press the dash to close it"
But if you use iOS 3 or less when you press ipod touch button it close running apps and go to your home page.