Your website consists of several layers – structure, data design, content, and functionality. Everything you click, interact, and customize on a website is user interface design. This user-centered functionality is designed by the frontend developer. The frontend developer uses a combination of client-side scripts as well as frameworks and markup languages to create an environment in which you can experience the aura of content, layout, and interaction.
At this point, creating any web application is impossible without interface development, so the interface is one of the most important parts of the web development process on par with the backend. Before the backend handles client requests, those requests are handled by interface scripts.