How would my friend install my iOS application without App Store?
You can share apps you develop by means of Ad-Hoc distribution. This involves adding the UDID of their device to your developer account (and consequently a provisioning profile) which lets you install the app on devices outside of the App Store.

For more information on Ad-Hoc distribution, see:


https://developer.apple.com/library/ios/documentation/IDEs/Conceptual/AppDistributionGuide/TestingYouriOSApp/TestingYouriOSApp.html


Apple does not operate a private App Store for non-apple use other than the custom business store and it's unlikely individuals would be accepted into that program so you have to self host the content as described above.