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 gapcontinue="Все_о_работе_с_базами_данных" />
  </query-continue>
  <query>
    <pages>
      <page pageid="6" ns="0" title="Все о FreeBSD">
        <revisions>
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">* [[Локализация FreeBSD на UTF-8]]</rev>
        </revisions>
      </page>
      <page pageid="4" ns="0" title="Все о Linux">
        <revisions>
          <rev contentformat="text/x-wiki" contentmodel="wikitext" xml:space="preserve">* [[Шифрование разделов dm-crypt, ключ шифрования на другом сервере на HTTP]]</rev>
        </revisions>
      </page>
    </pages>
  </query>
</api>