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="Bill_Houston_-_The_King_Of_White_Otter_Lake_front.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2388" ns="6" title="File:B&amp;WGardenscloseup.jpg" />
      <page pageid="3328" ns="6" title="File:BNHindiesshow.jpg" />
      <page pageid="3208" ns="6" title="File:Backroads.JPG" />
      <page pageid="2548" ns="6" title="File:Baycore-cover-volume1.jpg" />
      <page pageid="2073" ns="6" title="File:Baycorelogo.gif" />
      <page pageid="4425" ns="6" title="File:Bill Houston.jpg" />
      <page pageid="4414" ns="6" title="File:Bill Houston - Bring Back The Music front.jpg" />
      <page pageid="4427" ns="6" title="File:Bill Houston - Christmas Time Is Coming front.jpg" />
      <page pageid="4421" ns="6" title="File:Bill Houston - North Of Superior front.jpg" />
      <page pageid="4420" ns="6" title="File:Bill Houston - Open Spaces.jpg" />
    </pages>
  </query>
</api>