title: Difference between Document and document
body: <p>I had thought <code>Document</code> and <code>document</code> was always the same.</p>
  
  <p>But the console shows, <code>Document</code> is a <code>function</code> in chrome,</p>
  
  <p>while <code>document</code> is a <code>object</code>. Why?</p>
  
  <p>Why is the former used?</p>
  
  <p>I've searched SO, but I didn't get the answer and I <a href="https://www.google.co.in/search?q=difference+between+Document+and+document&amp;rlz=1C1DFOC_enIN576IN576&amp;oq=difference+between+Document+and+document&amp;aqs=chrome..69i57j0l5.12700j0j7&amp;sourceid=chrome&amp;espv=210&amp;es_sm=122&amp;ie=UTF-8" rel="nofollow">googled</a>, but still I didn't get my answer.</p>
  
  <p>And how to use the <code>Document</code> since it is a function?</p>