title: What does "@UIApplicationMain" mean?
body: <p>I just created my first Swift project, in the <code>AppDelegate.swift</code> there is a line above a class declaration - why is it there?!</p>
  
  <pre><code>...
  import UIKit
  import CoreData
  
  @UIApplicationMain // &lt;- WHY IS IT HERE?
  class AppDelegate: UIResponder, UIApplicationDelegate {
  ... 
  </code></pre>