Using Ruby Class and Module Differently

Create a module when you want to synthesize methods that span multiple classes instead of inheritance.

class=>can be instantiated.inheritable.
module=>Unable to instantiate.Namespace and method container.The method can be mixed in.

Rails often use ActiveSupport::Concern to create modules.

[Rails] ActiveSupport::Concern Reasons for Existence - Qiita

For example, if you implement only the upload function as concern on the controller that uploads files, it's a versatile application.