How does the refinement area work?

This is essentially a snippet from Ruby Metaprogramming 2. They obscure this example in this section, but there is really no explanation.

module MyRefinement
  refine MyClass do
    def my_method
      "refined"
    end
  end
end

class MyClass
  def my_method
    "original"
  end

  def another_method
    my_method
  end
end

using MyRefinement

obj = MyClass.new

puts obj.my_method       #=> "refined"
puts obj.another_method  #=> "original"

      

        
        
        
      

    

Why isn't it clarified when you call my_method

from another method?