In MVC design mode:

C stands for Controller, which is responsible for communication control between user interface and business logic layer. On the one hand, it interprets input from user interface, recognizes user actions (such as clicking buttons), and calls methods in corresponding Model; on the other hand, it handles events from Model and returns execution results, and calls appropriate View to display to users. The Controller is mainly completed by Servlet.

M stands for Model, which is responsible for the business logic realization of the whole solution, and the underlying database is also accessed and operated by Model;

V stands for View, which is responsible for the presentation of the system to users, mainly completed by HTML and JSP;