title: LESS differences between mixin and extend
body: <p>As stated in the title, I'm looking for a clear explanation regarding the differences between <code>mixin</code> and <code>extend</code> in <code>LESS</code>.</p>
  
  <p>Code examples &amp; live demo (i.e. on <a href="http://codepen.io/" rel="nofollow">codepen.io</a>) are more than welcome.</p>