title: What is Glew, Glut and glfw3? Which ones are deprecated in Opengl 3/4
body: <p>I have been reading online about how OpenGl 3 and 4 differ greatly from the previous versions.</p>
  
  <p>Some tutorials ask to:</p>
  
  <pre><code>#include &lt;GL/glew.h&gt;
  </code></pre>
  
  <p>Others will have:</p>
  
  <pre><code>#include &lt;GLUT/glut.h&gt;
  </code></pre>
  
  <p>What is <code>Glew</code>, <code>Glut</code> and <code>glfw3</code>? Which ones are deprecated and which ones are used in modern opengl?</p>