A jailbreak, in the context of computing, is a jargon expression for the act of overcoming limitations in a computer or device that was original put there for security, administrative or marketing reasons.
The jargon term is today mostly used to describe using software exploits to remove software restrictions imposed by Apple’s operating system. iOS jailbreaking permits root access to the iOS file system and manager, enabling the user to download applications, extensions and themes which are not available on the Apple App Store.
The main motivation of iOS jailbreaking is to expand a device’s feature set which is limited by Apple and its App Store.
However, this general motivation of breaking free of Apple’s perceived censorship of content and applications can be further categorised into device customisation, use of device on multiple carriers, installation of malware, and software privacy.
A form of privilege escalation, iOS jailbreaking started as soon as the original iPhone launched in 2007, continuing to the present day.