HTML documents use specific tags to structure and format text. The <html> tag forms the overall structure with <head> for metadata and <title>, and <body> for visible content. Headings are sized with <H1> through <H6> tags to structure sections and subsections. Paragraphs use the <P> tag and the <br> tag inserts line breaks. The <address> tag contains contact information. Comments can be added between <!--- and --> tags.