Your understanding of semantic HTML?

Do the right thing with the right label
html semantically structured so that the page content, structure is more clear, easy to browsers, search engines parse
also available in one document format even in the absence of css style case, and is easy to read
Search engine crawlers also relies on HTML tags to determine the weight of each keyword contextual and heavy, which will help SEO
to make the source code to everyone on the site easier to block a site, easy to maintain reading comprehension.