Two options are provided for testing your application.
Using an AdHoc certificate is a good option when only you or other developers on the team want to quickly install and check a build, as the builds can easily be exported by AppGameKit and installed directly onto your device.
An App Store certificate lets you upload your app to the App Store. If you take this option you can invite people to test your app using Apple's testing system called TestFlight. Anyone invited to test will receive an email. Clicking the link on the email will allow the user to install the app and test it. This approach bypasses having to manually install an app and makes it easier to test on multiple devices.
You can use whichever option is most suitable for your testing requirements, or both if necessary.