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="Bear_route.jpg" />
  </query-continue>
  <query>
    <pages>
      <page pageid="6790" ns="6" title="File:B-ball.png" />
      <page pageid="6116" ns="6" title="File:B ik1.png" />
      <page pageid="5631" ns="6" title="File:Baa analog.jpg" />
      <page pageid="5966" ns="6" title="File:Bastion.png" />
      <page pageid="5962" ns="6" title="File:Bastion Queen Anne.png" />
      <page pageid="6092" ns="6" title="File:Bat mbj.png" />
      <page pageid="1423" ns="6" title="File:BePipe.zip" />
      <page pageid="6279" ns="6" title="File:Bear1 mapkb.jpg" />
      <page pageid="6310" ns="6" title="File:Bear1 route.jpg" />
      <page pageid="6285" ns="6" title="File:Bear mapkb.jpg" />
    </pages>
  </query>
</api>