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:List formatting and function templates" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page ns="14" title="Category:Lists of cities in the Christian States" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page ns="14" title="Category:Lists of countries" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page ns="14" title="Category:Lists of law enforcement agencies" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page ns="14" title="Category:Lists of places in the Christian States" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page ns="14" title="Category:Lists of populated places by country" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page ns="14" title="Category:Lists of populated places in the Christian States" missing="" contentmodel="wikitext" pagelanguage="en" />
      <page pageid="57013" ns="14" title="Category:Listonia" contentmodel="wikitext" pagelanguage="en" touched="2019-02-04T04:10:13Z" lastrevid="622811" counter="1760" length="47" new="" />
      <page pageid="42930" ns="14" title="Category:Lists" contentmodel="wikitext" pagelanguage="en" touched="2018-10-02T20:05:24Z" lastrevid="457596" counter="2323" length="55" new="" />
    </pages>
  </query>
</api>