Apple iOS devices are only able to install apps from the Apple App Store. Users may use jailbreaking techniques to install their own versions of the operating system on their devices that allows the installation of unapproved apps. Geofencing is a technique that triggers notifications or events when a phone enters or leaves a defined geographic area. Carrier unlocking allows a phone to be moved between cellular service providers. Tethering allows phone users to use the phone as a mobile hotspot for laptops and other devices