A lot of people have asked me what UI/UX is lately, how they relate, and whether or not they’re interchangeable.
UI and UX relate, but they’re very different.
UI is the User Interface. It’s the part of the technology/product/software that the user interacts with. In other words, it’s the front-facing part of the product. At the core of UI (for the web) includes such things as the Visual Design, Human-Computer Interaction, and Information/Content Architecture. It would be how links look, where headers, paragraphs and links are positioned, what the pipeline of user interaction is (Does the website load on a splash page? Is the website structured across multiple pages or a singular one? Etc.) The color palette, icons and font stack used would all be a part of a website’s UI. A good UI should be one that is not cluttered, easy to navigate, is parsimonious in the fact that the website’s purpose (whether it be for users to buy a product, learn about a topic, or click links to further pages on a website) gets through to the user in as little steps/resources as possible, and leaves the user with a pleasant browsing experience. That experience is where UX comes in.
UX, or User Experience, is how the user feels while interacting with the UI/product. Does the user feel confused or overwhelmed by a mountain of text describing things they don’t yet care to read, or do smart, truncated blurbs capture their attention with a ‘Read More’ link if they’re interested in knowing more? Are the links tiny and camouflaged against an ugly attention-stealing background color? Or are the links stylized as buttons that feel satisfying to hover over and click? Are the prices for a product/service listed first and foremost, or is there an eye-catching ‘Try for free!’ button that makes the user feel good about the product right away? These are the types of UI choices that elicit good or bad UX.
Thus, good UI can create good UX, and good UX is usually indicative of an effective UI.
TL;DR: UI is the interface with which the user interacts with the technology/product. UX is the feeling and experience that the user achieves when interacting with the UI of a product.