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>
    <allcategories accontinue="123" />
  </query-continue>
  <query>
    <allcategories>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">&quot;Nations&quot;</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">(name)</c>
      <c size="1" pages="1" files="0" subcats="0" xml:space="preserve">(page name of the tank, must be exact please) Media</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">/P templates</c>
      <c size="0" pages="0" files="0" subcats="0" xml:space="preserve">105 leFH18B2</c>
      <c size="9" pages="0" files="9" subcats="0" xml:space="preserve">105 leFH18B2 Media</c>
      <c size="5" pages="0" files="5" subcats="0" xml:space="preserve">110 Media</c>
      <c size="4" pages="0" files="4" subcats="0" xml:space="preserve">112 Media</c>
      <c size="5" pages="0" files="5" subcats="0" xml:space="preserve">113 Media</c>
      <c size="7" pages="0" files="7" subcats="0" xml:space="preserve">121 Media</c>
    </allcategories>
  </query>
</api>