UI (User Interface) and UX (User Experience) allow you to create a website or application that will be functional and easy to use. The selection and design of individual interface elements in the right way means that users can easily find the information they need. The correct UI / UX is a multi-stage process, during which it is necessary to create a loi-fi mock-up, hi-fi mock-up or other sketch illustrating what the site will look like. It is also necessary to test the mock-up or ready application for usability and possible errors.