title: Is there special meaning to an underscore (_) in Type Bounds?
body: <p>I'm trying to understand Scala's existential types.</p>
  
  <p>Is there any difference between:</p>
  
  <pre><code>def foo[X &lt;: Bar] = 3
  </code></pre>
  
  <p>and</p>
  
  <pre><code>def foo[_ &lt;: Bar] = 3
  </code></pre>
  
  <p>or are they something more than just unnamed type parameters?</p>