Are you wondering if you can install any app on your iOS device? The answer is yes, but it depends on the app. The vast majority of apps can only be installed through the App Store, and Apple doesn't offer an official way to install software outside the App Store. However, there are some alternative options available. One way to install applications that haven't been published in the Apple App Store is to use a program called TestFlight.
This is much more reliable than jailbreaking, and is officially approved by Apple. TestFlight is a tool for developers to test beta versions of their applications before they are formally released. BuildStore hosts useful and popular iOS applications that are not available on the App Store and handles all the necessary certificate signing via OTA from the backend. Be very careful with the applications you decide to download, check and recheck the background of these applications and the background of the developers who create them.
You can manually install applications on an iPhone by downloading them to iTunes on your computer desktop and then transferring them by updating the contents of the iPhone using a USB cable. Once you've applied the jailbreak, you can install almost any application you like. Apple also allows developers to load applications to their iPhone from Xcode, a software for creating applications for iPhone, so that they can test current applications or show their creations to friends and family. You can install applications from file synchronization services, such as Dropbox, as long as you enable this feature for the corresponding application.
Learning to manually install applications on the iPhone will teach you an additional way to install applications if you can't do it through the app store app on your iPhone. Adjust iTunes & purchase settings in the App Store and be sure to select Allow in the app installation settings. If you're just trying to get a few apps from outside the App Store that don't require any special system permissions, side-loading is a safer option. In general, you should only install apps outside of your phone's app store if you have a very good reason to do so. If BuildStore isn't an option for you, there are other alternative options for installing apps from outside the App Store.