So, you have found a need to deploy a custom app to the devices in your organization and have received the go-ahead to build one. Apple encourages organizations and their developers to sign up with its Enterprise Developer Program so that they can be granted the capability to build and distribute custom-built apps outside the App Store. Many IT departments have already signed up individuals to not only test a release of the operating system, but the tinkerers amongst us can also build open source apps for personal use, which can also be achieved with a standard, standalone developer account. You can find more information about this at https://developer.apple.com/enterprise/.

The process of tying the required certificates and identifiers for an app to the desired devices for testing is referred to as provisioning. Creating and managing provisioning profiles will not always be necessary; however, it depends on how close to in-house your actual development...