Jailbreaking is the process by which full execute and write access is obtained on all the partitions of iOS, iPadOS, tvOS and watchOS. It is done by patching /private/etc/fstab to mount the System partition as 'read-write'. This is entirely different from an unlock. Jailbreaking is the first action that must be taken before things like unofficial activation (hacktivation), and unofficial unlocking can be applied.
Older jailbreaks also included modifying the AFC service (used by iTunes to access the filesystem) to give full filesystem access from root. This was later updated to create a new service (AFC2) that allows access to the full filesystem.
Modern jailbreaks now include patching the kernel to get around code signing and other restrictions. These are called Kernel
Patches.
