title: Difference Between // and http://
body: <p>I know that <code>HTTP</code> is hyper text transfer protocol, and I know that's how (along with <code>HTTPS</code>) one accesses a website. However, what does just a <code>//</code> do? For instance, to access Google's copy of jQuery, one would use the url <code>//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js</code>, as opposed to <code>http://...</code>. </p>
  
  <p>What exactly is the difference? What does just <code>//</code> indicate?</p>
  
  <p>Thanks.</p>