(latest known version)
Self Service, or Jamf Self Service, is a component of Jamf Pro, which is the MDM that Apple uses to distribute apps to their employees. Self Service is available for download via the App Store for free, and is used by many companies, including Apple, which is arguably Jamf's largest customer. In order to gain access to Self Service, your device must be associated with a Jamf Pro Server, which in an Apple employees' case, is distributed via email when they first connect to Apple's VPN. Once they have downloaded the required MDM Profiles to their device, they will be able to access Self Service. Administrators, or high-ranking corporate managers, maintain different sets of apps, settings, and policies on different servers, which certain employees can then download via Self Service just like they could download an app from the App Store. Employees will only be able to see and download select apps that are available to them based upon their position at Apple.
Self Service Replaces Switchboard
Despite using Self Service and other Jamf Pro tools for a long time, Apple had never fully relied on them as a way of distributing apps, as they had been using their own proprietary app, Switchboard, as the main source of apps since the early days of iOS. In late 2020, Apple announced that they would be phasing out Switchboard for good, and that they would be completely replacing it with Self Service, which they have since done.
Self Service on iPadOS