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Without the appropiate styling, the semantic elements will not look any different from the headline elements.
HTML5 introduced a number of new elements that have a semantic meaning. Semantic elements are elements that have a meaning to the browser, and to screen readers for blind users. They are also useful for search engines to understand the structure of a page.
The header element is used for the header of a page or section. The nav element is used for the navigation menu of a page. The main element is used for the main content of a page. The section element is used for a section of a page. The article element is used for an article on a page. The aside element is used for content that is not directly related to the main content of a page. The footer element is used for the footer of a page or section.
Without the appropiate styling, the semantic elements will not look any different from the headline elements.