title: Use of AuthConfig, BundleConfig, FilterConfig , RouteConfig and WebApiConfig in App_Start() folder in MVC
body: <p>Can you please explain in detail, the use of App_Start() folder in MVC4?
  I see that this folder is actually not available in previous versions of MVC. 
  There are 5 files in this folder. </p>
  
  <ol>
  <li>AuthConfig</li>
  <li>BundleConfig,</li>
  <li>FilterConfig,</li>
  <li>RouteConfig,</li>
  <li>WebApiConfig.</li>
  </ol>