User-Centered Design

User-Centered Design (UCD) is the process of designing a tool, such as a website’s or application’s user interface, from the perspective of how it will be understood and used by a human user. Usability is important because it can make the difference between performing a task accurately and completely or not, and enjoying the process or being frustrated. It can  also mean the difference between the success or failure of a system.
The Four User Interfaces are: Graphical, Touch, Voice, and Augmented Reality.
Graphical User Interfaces relies on the sense of sight. These are things like buttons, icons, scrolling bars, desktops and menus.
Touch User Interfaces is a computer-pointing technology based upon the sense of touch. A TUI enables not only the sense of touch to innervate and activate computer-based functions, it also allows the user, particularly those with visual impairments, an added level of interaction based upon tactile or Braille input.
Voice User Interfaces makes human interaction with computers possible through a voice/speech platform in order to initiate an automated service or process. A VUI is the interface to any speech application.
Augmented Reality User Interfaces is the integration of digital information with the user's environment in real time. Unlike virtual reality, which creates a totally artificial environment, augmented reality uses the existing environment and overlays new information on top of it.