What does jail breaking mean?

Answer 1

Jailbreaking is a process that allows iPhone and iPod Touch users to run unofficial code on their devices bypassing Apple's official distribution mechanism, the App Store. Once jailbroken, iPhone users are able to download many applications previously unavailable through the App Store via unofficial installers such as Cydia, Rock App, Icy, and Installer. Cydia is popular with users whilst Rock App has a small catalog of mainly paid apps. Icy and Installer are officially unsupported by their developers and rarely used. Cydia founder Jay Freeman estimates that 8.5% of all iPods and iPhones are jailbroken.[1] A jailbroken iPhone or iPod Touch is still able to use and update apps downloaded and purchased from Apple's official App Store.

Jailbreaking is distinct from SIM unlocking, which is the process by which a mobile device is made compatible with telephone networks with which it was not specifically licensed to be used. Jailbreaking, while not illegal, gives a user the ability to install cracked and pirated apps, which is illegal. Jailbreaking, according to Apple, voids Apple's warranty on the device, although this is quickly remedied by restoring the device in iTunes