title: What does `::` do in C++ language?
body: <p>I found a C++ file in PARSEC benchmark suite and saw some functions like this:</p>
  
  <pre><code>long Rng::rand()
  {
      return _rng-&gt;randInt();
  }
  </code></pre>
  
  <p>what does the <code>::</code> in the name of the function do here?</p>