Semantic HTML tags define content meaning for both browsers and developers, replacing generic `<div>` elements with purpose-built tags like `<header>`, `<nav>`, and `<article>`. This approach clarifies document structure, improves code readability, and aids search engines in parsing content hierarchy.

Using semantic markup directly boosts SEO by providing clearer context for crawlers and enhances accessibility for screen readers. It creates a clean, professional layout that's easier to maintain long-term, moving beyond presentational `div` soup to a standardized, meaningful structure.

Key tags include `<main>` for primary content, `<section>` for grouping, and `<time>` for dates. While they offer fewer default styles, the long-term benefits for code readability and cross-device compatibility outweigh the initial learning curve, especially as browser support for standards solidifies.