iOS Jailbreaking is a process that allows devices running Apple's iOS operating system (such as the iPad, iPhone, iPod Touch, and recently Apple TV) to gain full access (root access) to all features of the said operating system, thereby removing limitations imposed by Apple. Once jailbroken, iOS users are able to download additional applications, extensions and themes that are unavailable through the official App Store, via installers such as Cydia), one of a number of current means for older iPhones. A jailbroken iPad, iPhone or iPod Touch running iOS can still use the App Store and iTunes and other normal functions, such as making telephone calls.
Under the DMCA of 2010, jailbreaking is legal in the United States, although Apple may claim it to void your warranty. It is also legal in many other countries including those of the EU. The jailbreaking process, however, can be quickly and easily reversed by restoring the operating system through iTunes. Cydia creator Jay Freeman estimates that more than 10% of all iPhones are jailbroken.
An issue that confuses many people is the difference between a tethered and an untethered jailbreak. Tethered jailbreaks are often released first, but as the kernel is not patched, the device must be connected to a computer every time it needs to be booted into a jailbroken state. An untethered jailbreak is superior in that it allows the device to be powered off and rebooted without affecting the jailbreak, not requiring the use of a computer each time. Jailbreaking is different from SIM unlocking, which, once completed, means that the mobile phone will accept any SIM card without restriction, thus allowing the user access to alternative phone companies.
