MVC (Model-View-Controller) is a design pattern commonly used in PHP web development to separate the concerns of an application into three main components: the model, the view, and the controller.

The model represents the data and the business logic of the application. It is responsible for fetching data from a database, manipulating it, and providing it to the other components of the application. The model typically consists of classes and objects that handle data persistence and validation.

The view is responsible for rendering the user interface and presenting the data to the user. It consists of HTML templates and may use a template engine to generate dynamic content. The view is typically controlled by the controller, which provides it with the necessary data.

The controller is responsible for handling user requests and coordinating the flow of data between the model and the view. It receives user input from the view, interacts with the model to fetch or update data, and then updates the view accordingly. The controller is the main entry point of the application and serves as the intermediary between the model and the view.

In a PHP MVC application, the routing mechanism is used to map incoming requests to the corresponding controller methods. The controller then processes the request, interacts with the model if needed, and determines the appropriate view to render. After the view is rendered, it is sent back to the client as a response.

The MVC design pattern promotes the separation of concerns and the modularity of an application, making it easier to maintain, test, and understand. It also facilitates code reusability and promotes a clean and organized code structure.