Semantic HTML refers to the proper use of HTML elements that clearly convey content meaning and structure. Instead of <div> and <span>, it uses meaningful elements like <header>, <nav>, <main>, <article>, and <section>.

Semantic HTML benefits both SEO and accessibility. Search engines can better understand page structure, and screen readers can recognize each section as landmarks. HTML5 semantics guides cover these topics in detail.

Proper heading hierarchy (<h1> through <h6>) is also important. Using headings in logical order without skipping levels clarifies document structure.

From a character count perspective, semantic element tag names are longer than <div>, but the benefit of accurately conveying content meaning outweighs this. Web standards design books provide additional context.