title: On GitHub, what's the difference between reviewer and assignee?
body: <p>A feature added on Dec, 7, 2016, announced on GitHub blog, introduced the option <a href="https://github.com/blog/2291-introducing-review-requests">to add reviewers to a Pull Request</a></p>
  
  <p><a href="https://i.stack.imgur.com/0WXlq.gif"><img src="https://i.stack.imgur.com/0WXlq.gif" alt="GitHub Review Option"></a></p>
  
  <blockquote>
    <p>You can now request a review explicitly from collaborators, making it easier to specify who you'd like to review your pull request.</p>
    
    <p>You can also see a list of people who you are awaiting review from in the pull request page sidebar, as well as the status of reviews from those who have already left them.</p>
  </blockquote>
  
  <p>However, explicit setting a reviewer for a PR was already done by assigning people (<em>assignees</em> option).</p>
  
  <p>With both options now available, what's the role of each option since they both share the same end goal?</p>