The difference between User Interface (UI) and User Experience (UX) is that UI refers to the aesthetic elements by which people interact with a product, while UX is about the experience a user has with a product or service. So, UI focuses on visual interface elements such as typography, colors, menu bars, and more, while UX focuses on the user and their journey through the product.
Once the foundation is in place, you can start thinking about the interior design: hanging pictures in an attractive way, picking a style of furniture that suits the color of the wallpaper, organizing the kitchen utensils so they’re easy to reach without making the room look messy.
This example gives you a rough analogy of how design responsibilities are split between UX designers and UI designers working on a product: first, the logical flow of actions and fundamental parts are put in place, then the visual details are defined.
It also gives you a sense of how the collaboration works, with UX designers handing their work and recommendations over to the UI team once core concepts are tried and tested.