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>
    <links plcontinue="1|0|Under-18_Premier_League_Cup" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <links>
          <pl ns="0" title="EFL Trophy" />
          <pl ns="0" title="England" />
          <pl ns="0" title="FA Youth Cup" />
          <pl ns="0" title="Premier League 2" />
          <pl ns="0" title="Premier League Cup" />
          <pl ns="0" title="Premier League International Cup" />
          <pl ns="0" title="Professional Development League 2" />
          <pl ns="0" title="UEFA Youth League" />
          <pl ns="0" title="Under-18 League 2" />
          <pl ns="0" title="Under-18 Premier League" />
        </links>
      </page>
    </pages>
  </query>
</api>