The term "UI" in UI design refers to "user interface." The interface represents the visual appearance of an application. This includes the buttons users click on, the text they read, the images, sliders, text entry fields, and any other items that are interacted with by the user. Every micro interaction, including screen layout, transitions, interface animations, must be considered. All visual elements, interactions, and animations must be designed.
The UI designer is responsible for carrying out this task. They decide how the application will look. It is necessary to choose color schemes and button shapes - the width of lines and the fonts used in the text. An application's user interface is designed by UI designers.
Designers of user interfaces are graphic designers. They are primarily concerned with aesthetics. It is their responsibility to ensure that the application interface is attractive, visually stimulating, and appropriately themed to correspond to the purpose and/or persona of the application. Moreover, they must ensure that all visual elements are cohesive, both aesthetically and functionally.