An HTML Semantics developer ensures that web content is structured and labeled in a meaningful way. They use HTML semantic elements to reinforce the meaning of the content on web pages, rather than just for its appearance. This involves using tags appropriately for content such as articles, sections, headings, and navigation menus, among others. Their work plays a crucial role in improving website accessibility, search engine optimization, and cross-browser compatibility. They also maintain the consistency of the website design across different platforms. The developer must stay updated with the latest trends in HTML semantics to enhance user interaction.