A Simple Example 


  <UL> 
    <LI>paragraphs (P), 
    <LI>unordered lists (UL),
    <LI>list items (LI),
    <LI>headings (H1 -- H6)
  </UL>

  • paragraphs (P),
  • unordered lists (UL),
  • list items (LI),
  • headings (H1 -- H6)

Tags mark blocks of text for meaning (paragraphs, lists, etc).

There are rules for writing "correct" HTML, and for creating universally-accessible HTML documents.