The three aspects are Identifiers, Device, and then Provisioning Profile. Visit Apple Developers to manage these.
In Profiles -> Edit ensure certificates and correct device are checked before saving and downloading profile.
Once downloaded, open which loads into Keychain and Xcode.
Developer Certificate Can the user build the app
Distribution Certificate Can the user build the app in a way that could be consumed by Apple
App Store Certificate Can the user upload the build to Apple