CodeIgniter is an open-source web application framework that enables developers to create dynamic and interactive web applications using PHP. It is a powerful framework that helps developers to build feature-rich applications quickly and easily.

CodeIgniter web development follows the Model-View-Controller (MVC) architectural pattern, which separates application logic, presentation, and data layers into three components. This separation ensures that changes to one component do not affect the other components, which can make it easier to maintain and scale the application over time.