title: Can someone explain to me what the Builder Class does in Flutter?
body: <p>The documentation is very confusing and vague. Here is what it states:</p>
  
  <p><strong>Builder class</strong></p>
  
  <blockquote>
    <p>A platonic widget that calls a closure to obtain its child widget.</p>
  </blockquote>
  
  <p>Here are my questions:</p>
  
  <ol>
  <li>What do they mean by "platonic"?</li>
  <li>What do they mean by "closure"?</li>
  <li>What exactly is the purpose of this class?</li>
  </ol>