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>
    <namespaces>
      <ns id="-2" case="first-letter" canonical="Media" xml:space="preserve">Media</ns>
      <ns id="-1" case="first-letter" canonical="Special" xml:space="preserve">Special</ns>
      <ns id="0" case="first-letter" content="" xml:space="preserve" />
      <ns id="1" case="first-letter" subpages="" canonical="Talk" xml:space="preserve">Talk</ns>
      <ns id="2" case="first-letter" subpages="" canonical="User" xml:space="preserve">User</ns>
      <ns id="3" case="first-letter" subpages="" canonical="User talk" xml:space="preserve">User talk</ns>
      <ns id="4" case="first-letter" canonical="Project" xml:space="preserve">Bioinformatics Core Wiki</ns>
      <ns id="5" case="first-letter" subpages="" canonical="Project talk" xml:space="preserve">Bioinformatics Core Wiki talk</ns>
      <ns id="6" case="first-letter" canonical="File" xml:space="preserve">File</ns>
      <ns id="7" case="first-letter" subpages="" canonical="File talk" xml:space="preserve">File talk</ns>
      <ns id="8" case="first-letter" canonical="MediaWiki" xml:space="preserve">MediaWiki</ns>
      <ns id="9" case="first-letter" subpages="" canonical="MediaWiki talk" xml:space="preserve">MediaWiki talk</ns>
      <ns id="10" case="first-letter" canonical="Template" xml:space="preserve">Template</ns>
      <ns id="11" case="first-letter" subpages="" canonical="Template talk" xml:space="preserve">Template talk</ns>
      <ns id="12" case="first-letter" canonical="Help" xml:space="preserve">Help</ns>
      <ns id="13" case="first-letter" subpages="" canonical="Help talk" xml:space="preserve">Help talk</ns>
      <ns id="14" case="first-letter" canonical="Category" xml:space="preserve">Category</ns>
      <ns id="15" case="first-letter" subpages="" canonical="Category talk" xml:space="preserve">Category talk</ns>
      <ns id="80" case="first-letter" canonical="Post" content="" xml:space="preserve">Post</ns>
      <ns id="81" case="first-letter" canonical="Talk Post" xml:space="preserve">Talk Post</ns>
      <ns id="82" case="first-letter" canonical="Request" content="" xml:space="preserve">Request</ns>
      <ns id="83" case="first-letter" canonical="Talk Request" xml:space="preserve">Talk Request</ns>
      <ns id="84" case="first-letter" canonical="Task" content="" xml:space="preserve">Task</ns>
      <ns id="85" case="first-letter" canonical="Talk Task" xml:space="preserve">Talk Task</ns>
      <ns id="86" case="first-letter" canonical="Client" content="" xml:space="preserve">Client</ns>
      <ns id="87" case="first-letter" canonical="Talk Client" xml:space="preserve">Talk Client</ns>
      <ns id="88" case="first-letter" canonical="Institute" content="" xml:space="preserve">Institute</ns>
      <ns id="89" case="first-letter" canonical="Talk Institute" xml:space="preserve">Talk Institute</ns>
      <ns id="90" case="first-letter" canonical="Mirror" content="" xml:space="preserve">Mirror</ns>
      <ns id="91" case="first-letter" canonical="Talk Mirror" xml:space="preserve">Talk Mirror</ns>
      <ns id="100" case="first-letter" subpages="" canonical="Private" content="" nonincludable="" xml:space="preserve">Private</ns>
      <ns id="101" case="first-letter" subpages="" canonical="Talk Private" nonincludable="" xml:space="preserve">Talk Private</ns>
      <ns id="102" case="first-letter" canonical="Education" content="" xml:space="preserve">Education</ns>
      <ns id="103" case="first-letter" canonical="Talk Education" xml:space="preserve">Talk Education</ns>
      <ns id="104" case="first-letter" canonical="Provider" content="" xml:space="preserve">Provider</ns>
      <ns id="105" case="first-letter" canonical="Talk Provider" xml:space="preserve">Talk Provider</ns>
      <ns id="106" case="first-letter" canonical="HTML" content="" xml:space="preserve">HTML</ns>
      <ns id="107" case="first-letter" canonical="Talk HTML" xml:space="preserve">Talk HTML</ns>
      <ns id="108" case="first-letter" canonical="AltUser" content="" xml:space="preserve">AltUser</ns>
      <ns id="109" case="first-letter" canonical="Talk AltUser" xml:space="preserve">Talk AltUser</ns>
      <ns id="110" case="first-letter" canonical="Publication" content="" xml:space="preserve">Publication</ns>
      <ns id="111" case="first-letter" canonical="Talk Publication" xml:space="preserve">Talk Publication</ns>
      <ns id="112" case="first-letter" canonical="Property" xml:space="preserve">Property</ns>
      <ns id="113" case="first-letter" subpages="" canonical="Property talk" xml:space="preserve">Property talk</ns>
      <ns id="114" case="first-letter" canonical="Type" xml:space="preserve">Type</ns>
      <ns id="115" case="first-letter" subpages="" canonical="Type talk" xml:space="preserve">Type talk</ns>
      <ns id="116" case="first-letter" canonical="Form" xml:space="preserve">Form</ns>
      <ns id="117" case="first-letter" subpages="" canonical="Form talk" xml:space="preserve">Form talk</ns>
      <ns id="118" case="first-letter" canonical="Concept" xml:space="preserve">Concept</ns>
      <ns id="119" case="first-letter" subpages="" canonical="Concept talk" xml:space="preserve">Concept talk</ns>
      <ns id="274" case="first-letter" canonical="Widget" xml:space="preserve">Widget</ns>
      <ns id="275" case="first-letter" subpages="" canonical="Widget talk" xml:space="preserve">Widget talk</ns>
      <ns id="420" case="first-letter" canonical="Layer" xml:space="preserve">Layer</ns>
      <ns id="421" case="first-letter" canonical="Layer talk" xml:space="preserve">Layer talk</ns>
      <ns id="500" case="first-letter" canonical="Report" content="" xml:space="preserve">Report</ns>
      <ns id="501" case="first-letter" canonical="Talk Report" xml:space="preserve">Talk Report</ns>
    </namespaces>
  </query>
</api>