Ordered and unordered lists are particularly useful when they are nested.

Nested lists are lists inside of lists. For example, here are nested lists of comic book movies:
  

<html>
 <body>
  <ul>
   <li>Best comic book movies:
    <ol>
     <li>The Dark Knight</li> 
     <li>Spider-Man 2</li>
     <li>Avengers: Infinity War</li>
    </ol>
   </li>
   <li>Worst comic book movies:
    <ol>
     <li>Howard the Duck</li> 
     <li>Superman IV</li>
     <li>Batman & Robin</li>
    </ol>
   </li>
  </ul>
 </body>
</html>
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