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>
    <alllinks galcontinue="Institute_for_Scientific_Information_(ISI)|67" />
  </query-continue>
  <query>
    <pages>
      <page pageid="3" ns="0" title="Program kształcenia" />
      <page pageid="6" ns="0" title="Strona testowa" />
      <page pageid="12" ns="0" title="Adiunkt" />
      <page pageid="21" ns="0" title="Lista czasopism punktowanych przez MNiSW" />
      <page pageid="34" ns="0" title="ECTS (European Credit Transfer and Accumulation System)" />
      <page pageid="62" ns="0" title="Impact Factor (IF)" />
      <page pageid="67" ns="0" title="Journal Citation Reports" />
      <page pageid="173" ns="0" title="Stypendium pierwsze" />
      <page pageid="203" ns="0" title="Walet" />
    </pages>
  </query>
</api>