title: What is the underscore "_" in JavaScript?
body: <p>I'm doing a redux tutorial, and I saw a call like this:</p>
  
  <pre><code>this._render();
  </code></pre>
  
  <p>and it's defined elsewhere as:</p>
  
  <pre><code>_render() {
      ....
  } 
  </code></pre>
  
  <p>What is the underscore "_"? Why is it used?</p>