What is jail breaking
IOS_jailbreaking


  Jailbreaking is a process that allows iPad, iPhone and iPod Touch users to install homebrew applications on their devices by unlocking the operating system and allowing the user root access. Once jailbroken, iPhone users are able to download many extensions and themes previously unavailable through the App Store via unofficial installers such as Cydia, Rock Your Phone and Icy Installer. A jailbroken iPad, iPhone or iPod Touch is still able to use the App Store and iTunes.


It is mostly done to escape the restrictive nature of the App Store. Once you have jailbroken an iPhone you are free to install a lot of software that apple would not normally allow. Such as modifying the lock screen to display useful information, or enabling multitasking on an iPhone 3G.