The “UI” in UI design stands for “user interface.” The user interface is the graphical layout of an application. It consists of the buttons users click on, the text they read, the images, sliders, text entry fields, and all the rest of the items the user interacts with. This includes screen layout, transitions, interface animations and every single micro-interaction. Any sort of visual element, interaction, or animation must all be designed. This job falls to UI designers. They decide what the application is going to look like. They have to choose color schemes and button shapes — the width of lines and the fonts used for text. UI designers create the look and feel of an application’s user interface. UI designers are graphic designers. They’re concerned with aesthetics. It’s up to them to make sure the application’s interface is attractive, visually-stimulating and themed appropriately to match the purpose and/or personality of the app. And they need to make sure every single visual element feels united, both aesthetically, and in purpose.
“UX” stands for “user experience.” A user’s experience of the app is determined by how they interact with it. Is the experience smooth and intuitive or clunky and confusing? Does navigating the app feel logical or does it feel arbitrary? Does interacting with the app give people the sense that they’re efficiently accomplishing the tasks they set out to achieve or does it feel like a struggle? So UX designers are also concerned with an application’s user interface, and this is why people get confused about the difference between the two. But whereas UI designers are tasked with deciding how the user interface will look, UX designers are in charge of determining how the user interface operates.