title: What are -moz- and -webkit-?
body: <pre><code>-webkit-column-count: 3;
  -webkit-column-gap: 10px;
  -webkit-column-fill: auto;
  -moz-column-count: 3;
  -moz-column-gap: 10px;
  -moz-column-fill: auto;
  </code></pre>
  <p>I am a beginner at CSS and when I was looking at some CSS code the other day, I found these lines. In the tutorials I used to learn CSS, I have never seen anything like these lines. What is the explanation for these lines? Or is there a source where I could learn to implement lines like these?</p>