The installation of applications on iOS devices through methods other than the official App Store constitutes a process known as alternative app installation. This typically involves transferring an application package directly to a device and installing it, bypassing the customary review and distribution mechanisms Apple provides. One instance of this is a developer installing their own app for testing purposes before submitting it to the App Store.
This practice offers developers greater control over distribution and allows users access to applications not approved for the App Store, either due to policy violations or niche functionality. Historically, the closed nature of the iOS ecosystem has limited such practices, restricting users to applications vetted and distributed solely through official channels. This alternative method allows for the exploration of software that Apple does not allow, therefore potentially broadening the functionality and customization of iOS devices.