title: What does a function with 2 values on the right side mean? (Model -> Html msg)
body: <p>I have encountered that in the guide:</p>
  
  <pre><code>viewValidation : Model -&gt; Html msg
  viewValidation model =
    let
      (color, message) =
        if model.password == model.passwordAgain then
          ("green", "OK")
        else
          ("red", "Passwords do not match!")
    in
      div [ style [("color", color)] ] [ text message ]
  </code></pre>
  
  <p>So this is a function, which takes the <code>Model</code>. 
  <code>Html msg</code> usually looks to me like we are calling the function <code>Html</code> with the argument <code>msg</code>.</p>
  
  <p><code>msg</code> doesn't seem to play any role in any other part of the <code>viewValidation</code> function, though. So what does it mean and what is it for in this case?</p>