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-continue>
    <allfileusages gafcontinue="Calendar-module-settings.png|1328" />
  </query-continue>
  <query>
    <pages>
      <page pageid="18" ns="0" title="Fields Manager" />
      <page pageid="47" ns="0" title="JReviews Code Overrides" />
      <page pageid="52" ns="0" title="Category Layout Manager" />
      <page pageid="164" ns="0" title="How to edit the JReviews language files" />
      <page pageid="533" ns="0" title="Setup Twitter integration" />
      <page pageid="560" ns="0" title="Using the Banner Field Type" />
      <page pageid="578" ns="0" title="New Themes in JReviews 2.3" />
      <page pageid="669" ns="0" title="How to output user fields from Community Builder in JReviews themes" />
    </pages>
  </query>
</api>