You are looking at the HTML representation of the XML format.
HTML is good for debugging, but probably is not suitable for your application.
See complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allcategories gacfrom="List-Class biography articles" />
  </query-continue>
  <query>
    <pages>
      <page ns="14" title="Category:List-Class British royalty articles" missing="" />
      <page ns="14" title="Category:List-Class biography (actors and filmmakers) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (arts and entertainment) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (military) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (musicians) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (peerage) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (politics and government) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (royalty) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (science and academia) articles" missing="" />
      <page ns="14" title="Category:List-Class biography (sports and games) articles" missing="" />
    </pages>
  </query>
</api>