iOS is Apple’s operating system for mobile devices such as the iPhone and iPad.  Unlike Android, the iOS operating system cannot be customized and is closely controlled by Apple.  To develop mobile apps for iOS, developers use the iOS SDK, the XCode IDE and Objective-C.  These are the tools used to create a native iOS application that can be deployed on Apple’s App Store for download by your customers.  As an alternative to native iOS development, unifying mobile technologies such as PhoneGap and Xamarin allow a single codebase to be written but compiled to work on both iOS and Android.