You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page ns="14" title="Category:Lists of American politicians" missing="" />
      <page ns="14" title="Category:Lists of United States companies by industry" missing="" />
      <page ns="14" title="Category:Lists of college bowl games by team" missing="" />
      <page ns="14" title="Category:Lists of defunct sports teams" missing="" />
      <page ns="14" title="Category:Lists of people by cause of death" missing="" />
      <page ns="14" title="Category:Lists of supermarkets" missing="" />
      <page ns="14" title="Category:Lists of television channels by region" missing="" />
    </pages>
  </query>
</api>