Semantic HTML is about using HTML elements for their intended purpose, like <header>, <article>, and <footer>, instead of relying solely on <div> and <span>. This practice improves accessibility by providing context to screen readers and search engines. For example, a screen reader can navigate a page more efficiently when it knows which elements represent navigation, main content, or a footer. By writing semantic HTML, you make your website more inclusive and easier to understand for all users.