I have some ipa files and it turns out that I can install directly on my device without having to do anything unusual, just itunes. These apps are not in the app store, so I guess they've done something with Xcode or with the ipas, right? How is this possible?

When I pass the apps I've done to some beta testers I have to ask IDs and after putting it in the certificate, it can be installed, but if not, no.

So anyone have any idea? What happened?

If you have an Enterprise account, you still need the ID's of the testers, right?

sorry for my bad english, but at least I try! 

Greetings and thanks!