Mobile app UI design refers to the visual and interactive elements of a mobile application's user interface. It encompasses the layout, color scheme, typography, icons, buttons, and overall look and feel of the app. The primary goal of mobile app UI design is to create a user-friendly and aesthetically pleasing interface that enhances the user experience and makes it easy for users to navigate, interact with, and understand the app's functionality. Effective UI design considers factors like usability, accessibility, and consistency to ensure a seamless and enjoyable interaction between the user and the app.