test.rb

class Person
  
  @var = 13 # instance_class_variable
  @@var = 15 # class variable

  def self.class_method
    puts "access from class method: #{@var}"
    puts "access from class method: #{@@var}"
  end
  
  def instance_method
  	puts "access from instance method: #{@var}"
  	puts "access from instance method: #{@@var}"
  end
  
end

Person.class_method

x = Person.new
x.instance_method