What defines semantic HTML elements?

Semantic HTML elements are defined by their ability to clearly describe their meaning in a way that is both human-readable and machine-readable. These elements provide important context about their content and purpose, aiding in accessibility and search engine optimization. For instance, using elements like <header>, <article>, and <footer> helps convey the structure and organization of a web page, allowing browsers and assistive technologies to interpret the information more effectively.

In contrast, options suggesting that semantic elements are either invisible to machines, purely for layout, or obsolete do not align with the fundamental principles of semantic HTML. Visual elements lacking semantic significance do not enhance content understanding and can complicate the rendering of web pages for both users and machines. Thus, the focus on meaning and context in semantic HTML is essential for fostering a more accessible and structured web.