title: Variables after the colon in a constructor
body: <p>I am still learning C++ and trying to understand it. I was looking through some code and saw:</p>
  
  <pre><code>point3(float X, float Y, float Z) :
  x(X), y(Y), z(Z)  // &lt;----- what is this used for
  {
  }
  </code></pre>
  
  <p>What is the meaning of the "x(X), y(Y), z(Z)" sitting beside the constructor's parameters?</p>