Why CodeIgniter is called as loosely based MVC framework?

While we create a new application in the Codeigniter framework there is no need of following any strict pattern that is the main reason why Codeigniter is called a loosely based MVC framework. To build any application we can build the model with view and controllers only. In the case of a Codeigniter controller plays an important role but view and model are optional. It's called a loosely based framework. So, in short, it means that a website can also be built without a model. The advantage of using the MVC framework is that it is easy to manage and can be maintained by anyone easily.