title: algorithm complexity - what double star means
body: <p>Does anybody know what means doubled-star in complexity algorithm like this <code>O(N**3)</code>? I found that one in PHP's <a href="http://php.net/manual/en/function.similar-text.php" rel="nofollow">similar_text()</a> function and do not understand it.</p>
  
  <p>thx</p>