Jailbreak
Jailbreaking is a process that removes restrictions placed on a device by the manufacturer, often by exploiting a software bug. It most commonly refers to granting root access on an iPhone or iPad, but it also can apply to other devices like game consoles. Users typically jailbreak their devices to install applications from outside sources, bypassing official app stores.
The jailbreaking process requires exploiting a vulnerability on the device, usually in its firmware or operating system. Once hackers discover an exploitable vulnerability for a particular device, they make and distribute a software tool to automate the process. Since device manufacturers routinely patch these vulnerabilities, each jailbreaking method usually only works on a single device generation or operating system version. Most methods involve connecting the device to a computer by a USB cable, running the jailbreaking tool on the computer, and restarting the device when prompted. The jailbreaking tool exploits the vulnerability it was designed for and provides the user with root access. Most will also install a package manager that the user can use to install applications.
Jailbreaking a device does come with some drawbacks. First, any operating system or firmware update will remove the jailbreak, making the user choose between up-to-date software or maintaining root access. Second, installing software from unknown sources may also introduce malware. A jailbreak's modifications to the system software may also lead to instability and crashes. Finally, some jailbreak methods require the device to restart while connected to a computer running the jailbreak tool to maintain it and are known as "tethered" jailbreaks.
NOTE: When removing these restrictions on an Android device, the process is known as "rooting." However, the process is generally much easier, as most Android device manufacturers openly allow advanced users to root their devices.