The Apple Developer Account Enrollment Guide covers the process of the Apple Developer account creation and enrollment.
If the users want to make their apps available on the App Store, then they have to log in with their Apple Id and enroll their Apple Developer Account in the Apple Developer Program. If the users do not have the Apple Id, then they have to create the new one.
The Apple Developer Program provides everything that the users need to build and distribute their apps to Apple customers around the world. The paid Apple Developer Account is used to sideload apps on the iPhone, iPad, and Apple TV, and also to deploy apps to the App Store.
The users can use the Apple Developer account to test their apps on their registered devices.
Tip : Sideloading, intends installing an application package available in the APK format on an Android device.