title: Bootstrap arrow that's attached to div
body: <p>I'm very very new to bootstrap and front-end frameworks in general. But, I am able to notice the characteristics that sites that use bootstrap have in common. The following picture contains something that I find to be very ubiquitous amongst bootstrap sites. The downward (or any direction) blue arrow that's pointing the the text below it is what I'm referring too.</p>
  
  <p>I used firebug to inspect the elements and found it to be something that was relevant to the <code>.hero-unit</code> div. </p>
  
  <p>How exactly does this work and how is it accomplished?</p>
  
  <p><img src="https://i.stack.imgur.com/lB0ux.png" alt="Downward arrow"> </p>