title: How does Facebook real time works?
body: <p>I don't know how to formally state this question as i don't know what is actually happening here.
  Whenever any user comments on my post, facebook makes a request like below to display that comment without me doing anything.How do they do it?</p>
  
  <pre><code>https://0-edge-chat.facebook.com/pull?channel=p_100009456028304
  </code></pre>
  
  <p>This cannot be push notification as they are are making a pull request constantly(i checked using developer tools available in browsers, although i 
  am not sure about if it is push notification or not).They are constantly making a pull request to above URL.What this technology is called?
  <a href="https://i.stack.imgur.com/PX9kx.png" rel="noreferrer"><img src="https://i.stack.imgur.com/PX9kx.png" alt="Constant request"></a>
  Can someone please help me understand this.
  Maybe this question is duplicate and already answered on stack overflow.But
  as i don't what this is, it's hard to search.(i tried but couldn't find anything)</p>