title: What is the difference between :before and ::before?
body: <p>I just saw a CSS code that included <code>::before</code> tag. I looked at <a href="https://developer.mozilla.org/en/CSS/:before" rel="noreferrer">MDN</a> to see what the <code>::before</code> is but I really didn't understand it. </p>
  
  <p>Can someone explain how it works? </p>
  
  <p>Does it make a DOM element before what we select by CSS?</p>