This show the difference between naming classes with the :: syntax or wrapping with an explicit module. Try and guess what will happen when you run the code below

class_load_test.rb

module C
  class B
    def initialize
      puts 'B'
    end
  end
end

module C
  class D
    def initialize
      puts 'D'
      B.new
    end
  end
end

class C::A
  def initialize
    puts 'A'
    B.new
  end
end

C::D.new
C::A.new