UID is the abbreviation for User Interface Design. It includes a series of screens, pages, buttons, icons, etc. that enable a person to interact with a website or an application.
UXD is the abbreviation for User Experience Design. User experience is much deeper than UI as it involves the internal experience that the user has as he/she interacts with every aspect of your company’s products or services.

UX, or user experience, is the process of designing and developing products and services that are easy to use, efficient, and enjoyable for the end-user. UXD helps your business achieve improved customer satisfaction, increased conversion rate, reduced development costs, and increased brand loyalty.