We can’t discuss UX without mentioning user interface (UI) because the two are often connected, and also frequently confused. UX is science-based and takes into account sociology. Think big picture.
User Interface is more graphically focused, with attention to the buttons on which a user clicks and the paths that follow. UI is the look and feel of a website, its responsiveness and interactivity. A visitor might have an excellent UI with your site but walk away with a disappointing experience upon learning you don’t have the content he or she is seeking.
Further, you’ll often hear about usability, another essential element of your website and app design. This refers to the utility of a site, whether it’s easy to use and has the features you need. You may also see references to this in terms of accessibility, providing resources for people with disabilities. For example, people with visual impairment rely on software that reads alternative text out loud to them, describing images on the screen.
This article from UserTesting.com explains the nuances in more detail. For now, take a gander at the below graphic for this “quick & dirty” explanation.