What are semantic HTML elements? Give examples.

Semantic HTML elements are tags that convey meaning about the content they contain, both to the browser and to developers. Non-semantic elements like <div> and <span> say nothing about their content. Semantic elements provide context. Examples include <header> (top of a page or section), <nav> (navigation links), <main> (primary content), <article> (self-contained content), <section> (thematic grouping), <aside> (sidebar content), <footer> (bottom of page), <figure> and <figcaption> (media with caption), and <time>. They improve accessibility, SEO, and code readability.