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>
    <allfileusages gafcontinue="Back.png|5357" />
  </query-continue>
  <query>
    <pages>
      <page pageid="552" ns="0" title="Hangeul step 2" />
      <page pageid="553" ns="0" title="Hangeul step 3" />
      <page pageid="554" ns="0" title="Hangeul step 4" />
      <page pageid="557" ns="0" title="Hangeul step 5" />
      <page pageid="558" ns="0" title="Hangeul step 6" />
      <page pageid="792" ns="0" title="Important 한자 2" />
      <page pageid="793" ns="0" title="Important 한자 3" />
      <page pageid="4581" ns="0" title="Hangeul quiz 1" />
      <page pageid="4616" ns="0" title="Hangeul step 4b" />
      <page pageid="4617" ns="0" title="Hangeul step 3b" />
    </pages>
  </query>
</api>