User Interface (UI) Design is the process of creating user-centric prototypical graphical user interfaces (GUIs), websites, mobile apps, and voice-controlled/gesture-controlled software applications. Whenever a user experiences or interacts with something on a screen or digital display, the look and feel was relayed via UI Design, or a designer implementing this practice.
This role of UI Designer has evolved out of the dissemination of online- and web-based content. As generations continue to adapt and evolve, we spend more time on devices connected to the Internet to consume content, media, games, etc. How does the content on screen get translated to the device? Is it usable? How many clicks does it take to do XYZ? Does it convey brand and messaging? Is it unconscious or conscious (i.e. does it distract me from what I want to do)? These questions get answered by UI Design.
UI Design goes hand-in-hand with User Experience (UX) Design, as the former is a focus on aesthetic and the latter on interaction, but they often cited as equivalent. There is much that goes into each specialty, and to combine them into one discipline is cutting the other one short of its full potential. It is easiest to picture UX Design enveloping UI Design, because UI is an aspect within the full scope of UX Design.
The process of UI Design from my perspective goes like this:
Have an initial meeting to go over the scope of the project and requirements for the end-product, which is expected to be developed via full-stack engineering.
Design an initial low-fidelity pass in Adobe Experience Design (Adobe XD) to represent prototypical interactions in a wireframe setting—relative to UX Design.
Assess continual feedback from the client until a high-fidelity mockup is ready to be explored. Design the mockup to represent a full-fledged application while incorporating aesthetic/brand decisions, interactions, assets, copy, and further changes.
Continue to support the UI project via front-end development of the interface.
“If a picture is worth 1000 words, a prototype is worth 1000 meetings.” — David & Tom Kelley
UI Design is one piece of the puzzle of creating usable and friendly interfaces, but serves as the basis for development while incorporating agile feedback. It is a step that should not be skipped as it pertains to aesthetic requirements and development revision time.