User experience (UX) design is the practice of shaping how a person feels and succeeds when using a product, from the first time they hear about it to using it daily — the term was popularized by researcher Don Norman at Apple in the early 1990s to describe the full scope of a person's interaction with a company and its products. User interface (UI) design is the visual and interactive layer within that experience: the buttons, icons, colors, typography, and spacing a person actually touches and sees on screen. A product can have a gorgeous UI but a confusing UX (users get lost even though every screen looks nice), or a clear UX with a rough UI (easy to use but unattractive) — strong products need both disciplines working together with product managers and engineers throughout development, not bolted on at the end.