CodeIgniter framework is based on MVC pattern. MVC is a software that gives you a separate logical view from the presentation view. Due to this, a web page contains minimal scripting.

Model - The Controller manages models. It represents your data structure. Model classes contain functions through which you can insert, retrieve or update information in your database.
View - View is the information that is presented in front of users. It can be a web page or parts the page like header and footer.
Controllers - Controller is the intermediary between models and view to process HTTP request and generates a web page. All the requests received by the controller are passed on to models and view to process the information.