Module vs class in ruby programming language

Modules are about providing methods that you can use across multiple classes - think about them as “libraries” (as you would see in a Rails app). Classes are about objects; modules are about functions. Class is mainly different from Module by 3 main methods: new, allocate, superclass.

The table below show you the different between them.

	Class	Module
instantiation	can be instantiated	can not be instantiated
usage	object creation	mixin facility. provide a namespace.
superclass	module	object
methods	class methods and instance methods	module methods and instance methods
inheritance	inherits behaviour and can be base for inheritance	No inheritance
inclusion	cannot be included	can be included in classes and modules by using the include command (includes all instance methods as instance methods in a class/module)
extension	can not extend with extend command (only with inheritance)	module can extend instance by using extend command (extends given instance with singleton methods from module)

Example codes

module A
  class B
    def initialize
      @ins_var = 1
    end
  end
end

a = A.new # undefined method new for A:Module
a = A::B.new
puts a.ins_var # 1