A jailbreak in the narrower sense is the removal of usage restrictions on iOS devices. To do this, the mobile device usually has to be connected to a computer with the corresponding jailbreak software.
The procedure is called "rooting" for Android devices. Usage restrictions that are caused by Apple's closed-world model can be circumvented by a jailbreak. Thus, "liberated" iPhones can also obtain mobile apps outside of the official Apple app store, which is not possible in the standard delivery state of the devices.
End devices with jailbreak can be a potential source of danger for corporate networks due to root access, access to the file system and the installation of unauthorized apps through alternative app stores. This is especially relevant in BYOD scenarios. In addition, devices with jailbreak lose their warranty claim and may suffer from system instability.