Swift is a multi-paradigm, compiled programming language developed by Apple for iOS and OS X development. wikipedia.org

The UIKit framework provides the classes needed to construct and manage an application's user interface for iOS. It provides an application object, event handling, drawing model, windows, views, and controls specifically designed for a touch screen interface.

Objective-C is a reflective, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. wikipedia.org

Mobile application development is the process by which application software is developed for low-power handheld devices, such as personal digital assistants, enterprise digital assistants or mobile phones. wikipedia.org

iOS (formerly iPhone OS) is Apple Inc.'s mobile operating system. Originally developed for the iPhone, it has since been extended to support other Apple, Inc. devices such as the iPod Touch, iPad, and Apple TV. wikipedia.org

Xcode is a suite of tools developed by Apple for developing software for Mac OS X and iOS, first released in 2003. wikipedia.org

Mobile application testing is a process by which application software developed for hand held mobile devices is tested for its functionality, usability and consistency. wikipedia.org

Code refactoring is a disciplined technique for restructuring an existing body of code, altering its internal structure without changing its external behavior, undertaken in order to improve some of the nonfunctional attributes of the software. wikipedia.org

A mobile application, also referred to as a mobile app or simply an app, is a computer program or software application designed to run on a mobile device such as a phone, tablet, or watch. wikipedia.org