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="0" title="Formal verification" missing="" />
      <page pageid="518" ns="0" title="Course" />
      <page pageid="634" ns="0" title="Health Occupations Students of America-Future Health Professionals" />
      <page pageid="511" ns="0" title="National Honor Society" />
      <page pageid="482" ns="0" title="Parent-Teacher Organization" />
      <page pageid="77" ns="0" title="School District 49" />
    </pages>
  </query>
</api>