title: Ruby modules - included do end block
body: <p>There is a module <code>MyModule</code>:</p>
  
  <pre><code>module MyModule
  
    extend ActiveSupport::Concern
  
    def first_method
    end
  
    def second_method
    end
  
    included do
      second_class_method
    end
  
    module ClassMethods
      def first_class_method
      end
  
      def second_class_method
      end
    end
  end
  </code></pre>
  
  <p>When some class <code>include</code>s this module, it will have 2 methods exposed as instance methods (<code>first_method</code> and <code>second_method</code>) and 2 class methods (<code>first_class_method</code> and <code>second_class_method</code>) - it is clear.</p>
  
  <p>It is said, that </p>
  
  <blockquote>
    <p><code>included</code> block will be executed within the context of the class that
    is including the module.</p>
  </blockquote>
  
  <p>What does it mean exactly? Meaning, when exactly would this method (<code>second_class_method</code>) be executed?</p>