title: Why https and www are in same URL?
body: <p>Some URLs have both <code>https</code> and <code>www</code>.
  What is the reason behind this?</p>
  
  <p>For example, <a href="https://www.facebook.com" rel="nofollow noreferrer">https://www.facebook.com</a> starts with <code>https://www</code>. Is this redundant?</p>