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>
    <pages>
      <page pageid="1" ns="0" title="Main Page">
        <images>
          <im ns="6" title="File:20150708MST 0130.jpg" />
          <im ns="6" title="File:Blank.png" />
          <im ns="6" title="File:Cd0b00 d92f75fa3e9445979ac32d86a85165bd.gif" />
          <im ns="6" title="File:Congress-and-more logo.png" />
          <im ns="6" title="File:IEEExplorer.gif" />
          <im ns="6" title="File:VDE Logo 4c.png" />
        </images>
      </page>
    </pages>
  </query>
</api>