class Dog
  def initialize(name)
    @name = name
  end

  def name=(a_name)
    @name = a_name
  end

  def name
    return @name
  end
end

d = Dog.new("Spot")
puts d.name

d.name = "Rover"
puts d.name

The Dog class above is equivalent to:

class Dog
  attr_accessor :name

  def initialize(name)
    @name = name
  end

end

In other words,  the line:

attr_accessor :name