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="Building Source Code" />
          <pl ns="0" title="Calling REST based Web services" />
          <pl ns="0" title="Calling SOAP Web services" />
          <pl ns="0" title="Configuration file" />
          <pl ns="0" title="ETL scenario language" />
          <pl ns="0" title="Installing and Configuring ETL Framework" />
          <pl ns="0" title="Redistribution and managing dependencies" />
          <pl ns="0" title="Running ETL Scenarios" />
          <pl ns="0" title="Using Eclipse" />
          <pl ns="0" title="Writing data integration and data migration scenarios" />
        </links>
      </page>
    </pages>
  </query>
</api>