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 pageid="1" ns="0" title="Main Page">
        <links>
          <pl ns="0" title="Code Coverage Tool for R" />
          <pl ns="0" title="Distributed Computing Working Group" />
          <pl ns="0" title="R Certification" />
          <pl ns="0" title="R Consortium and the R Community Code of Conduct" />
          <pl ns="0" title="R Native API" />
          <pl ns="0" title="R in Medicine" />
          <pl ns="0" title="R in Pharma" />
          <pl ns="0" title="Top Level Projects" />
        </links>
      </page>
    </pages>
  </query>
</api>