title: What does # mean in Mathematica?
body: <p>Does anyone know What # in for example <code>Root[-1 - 2 #1 - #1^2 + 2 #1^3 + #1^4 &amp;, 1]</code> means in Mathematica?</p>
  
  <p>Then what does <code>Root[-1 - 2 #1 - #1^2 + 2 #1^3 + #1^4 &amp;, 1]</code> exactly mean?</p>
  
  <p>Thanks.</p>