title: What are Subscriptions in RxJS and how do Observables interact with them?
body: <p>I don't have it very clear on how Observables and Subscriptions work. In particular how an Observable and its Subscriptions exchange information.</p>
  
  <p>So to make explicit questions: </p>
  
  <ul>
  <li>Does an Observable keep references to its Subscriptions? </li>
  <li>Does a Subscription keep a reference to the Observable that created it? </li>
  <li>Does an Observable "put" data in its Subscriptions or does a Subscription "poll" its Observable? </li>
  <li>How does the information exchange happen? </li>
  </ul>