what mattr_accessor rails module?

i couldn't unequivocally rails support nonetheless seems 'mattr_accessor' module inference 'attr_accessor' (getter & setter) normal flush class.

eg. class

class user
  attr_accessor :name

  def set_fullname
    @name = "#{self.first_name} #{self.last_name}"
  end
end

eg. module

module authentication
  mattr_accessor :current_user

  def login
    @current_user = session[:user_id] || nil
  end
end

this supporter slight presumption activesupport.