`:status` is a symbol.. like a string. Even though there aren't parenthesis, this is just a gross [but conventional] way of making a hash and passing it as a parameter to a function.

    {
      :json => Course.missing_course(params[:id])
      :status => 404
    }

This pattern is called the options hash. http://blog.ethanvizitei.com/2010/11/options-hash-classic-ruby-pattern.html