What is trailing closure syntax in Swift?
<p>Swift's <a href="https://docs.swift.org/swift-book/LanguageGuide/Closures.html#//apple_ref/doc/uid/TP40014097-CH11-ID102" rel="noreferrer">documentation on closures</a> states:</p>

<blockquote>
  <p>Swift’s closure expressions have a clean, clear style, with optimizations that encourage brief, clutter-free syntax in common scenarios. These optimizations include:</p>
  
  <ul>
  <li>Inferring parameter and return value types from context</li>
  <li>Implicit returns from single-expression closures</li>
  <li>Shorthand argument names</li>
  <li><strong>Trailing closure syntax</strong></li>
  </ul>
</blockquote>

<p>What exactly is "trailing closure syntax" for Swift closures?</p>