What UI really is (and how UX confuses matters)
People mix the terms UI and UX together. UX is tricky because it doesn’t refer to any one thing. Interface design, visual styling, code performance, uptime, and feature set all contribute to the user’s “experience.” Books on UX further complicate matters by including research methods and development methodologies. All of this makes the field confusing for people who want to understand the fundamentals.
That’s why I avoid teaching the term ’UX.’ It means too many things to too many different people. Instead I focus on individual skills. Once you understand the individual skills, you can assemble them into a composite system without blurring them together. For software design, the core skill among all user-facing concerns is user interface design.