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>
    <allpages apcontinue="Enigma_Machine_Key_Length" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="260" ns="0" title="Bletchley Park Working Aid" />
      <p pageid="65" ns="0" title="Copyright" />
      <p pageid="247" ns="0" title="Enigma" />
      <p pageid="152" ns="0" title="Enigma/Key Length" />
      <p pageid="253" ns="0" title="Enigma/Paper Enigma" />
      <p pageid="172" ns="0" title="Enigma/Sample Decrypts" />
      <p pageid="171" ns="0" title="Enigma/Sample Messages" />
      <p pageid="173" ns="0" title="Enigma/Sending and Receiving Messages" />
      <p pageid="279" ns="0" title="Enigma/Simulator Social Media" />
      <p pageid="165" ns="0" title="Enigma/Simulator User Guide" />
    </allpages>
  </query>
</api>