title: What does the SwiftUI `@State` keyword do?
body: <p>The <a href="https://developer.apple.com/tutorials/swiftui/handling-user-input" rel="noreferrer">SwiftUI tutorial</a> uses the <code>@State</code> keyword to indicate mutable UI state:</p>
  
  <p><code>@State var showFavoritesOnly = false</code></p>
  
  <p>It offers this summary:</p>
  
  <blockquote>
    <p>State is a value, or a set of values, that can change over time, and that affects a view’s behavior, content, or layout. You use a property with the @State attribute to add state to a view.</p>
  </blockquote>
  
  <ul>
  <li>What does the keyword mean, exactly?</li>
  <li>How does mutating a <code>@State</code> variable cause the view to be recomputed?</li>
  <li>How are other variables immutable within the <code>body</code> getter?</li>
  </ul>