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="Figure2.jpg|4215" />
  </query-continue>
  <query>
    <pages>
      <page pageid="2979" ns="0" title="Protected Site networking" />
      <page pageid="3965" ns="0" title="Monitoring Resource Usage of Jobs with cAdvisor" />
      <page pageid="4215" ns="0" title="Benchmarking procedure" />
      <page pageid="4435" ns="0" title="RAL Tier1 Incident 20180103 Atlas Data Server Failure" />
      <page pageid="4531" ns="0" title="Tier1 Operations Report 2018-11-20" />
    </pages>
  </query>
</api>