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>
    <pageswithprop gpwpcontinue="228" />
  </query-continue>
  <query>
    <pages>
      <page pageid="39" ns="0" title="Quick Start" touched="2016-02-04T15:23:03Z" lastrevid="4571" counter="13545" length="3955" />
      <page pageid="73" ns="0" title="Empezando con GXtest" touched="2014-08-22T11:59:18Z" lastrevid="4148" counter="39439" length="5260" />
      <page pageid="79" ns="0" title="Crear un Caso de Prueba con Datapools" touched="2014-08-22T12:31:04Z" lastrevid="4153" counter="22568" length="5599" />
      <page pageid="80" ns="0" title="Crear un Caso de Prueba Anidado" touched="2014-02-21T01:55:59Z" lastrevid="3525" counter="15431" length="2732" />
      <page pageid="102" ns="0" title="Crear un Caso de Prueba con Variables" touched="2014-03-28T17:31:56Z" lastrevid="3508" counter="16058" length="3733" />
      <page pageid="120" ns="0" title="Test Cases - XML" touched="2014-02-21T03:44:23Z" lastrevid="3554" counter="7222" length="44628" />
      <page pageid="142" ns="0" title="Help GXtest Designer" touched="2014-02-20T15:59:22Z" lastrevid="2740" counter="29219" length="1850" />
      <page pageid="143" ns="0" title="Help GXtest Manager" touched="2014-02-20T15:59:22Z" lastrevid="2783" counter="30826" length="1871" />
      <page pageid="206" ns="0" title="Empezando con GXtest Manager" touched="2016-04-22T18:00:45Z" lastrevid="4653" counter="15410" length="1567" />
      <page pageid="212" ns="0" title="Welcome" touched="2019-10-01T19:17:13Z" lastrevid="5000" counter="66427" length="3395" />
    </pages>
  </query>
</api>