What are HTML5 semantic elements and why are they important?

HTML5 introduced elements like <header>, <footer>, <nav>, <main>, <article>, <section>, <aside>, <figure>, and <time> that describe the meaning and purpose of content rather than just its appearance. They matter for three key reasons: Accessibility — screen readers use semantic landmarks to help users navigate pages. SEO — search engines understand content structure better, potentially improving rankings. Maintainability — code is easier to read and understand when structure is expressed semantically. A page built entirely with <div> tags is technically valid but conveys no structural meaning.