A Web developer is a kind of programmer who specializes in the development of applications relating to the World Wide Web or distributed network applications, which typically run protocols like HTTP from a Web server to a client browser using associated programming languages like HTML/CSS, C#, Ruby and PHP to name a few.
UX design refers to user experience design, while UI design stands for user interface design. Both of these are crucial to an IT product and need to work closely together. Despite being very integral to each other, the roles themselves are quite different, involving distinct processes. UX is User Experience.
Data science is a broad field that refers to the collective processes, theories, concepts, tools and technologies that enable the review, analysis and extraction of valuable knowledge and information from raw data.