I am pretty sure that if you are reading this book, you are already familiar with the MVC pattern, but for beginners, we will try to explain this in a few words.
MVC is defined as an architectural pattern, and it stands for Model-View-Controller; it is used mostly in web development, but it is widely applied in software that needs a Graphical User Interface (GUI). To make this introduction quick, let's explain these components:
Model: This is usually used as an abstraction layer, and validation for the tables of a database, but it can be used to handle any kind of logic within the application.
View: A view, usually, represents a template (can be an HTML file) that the controller will render.
Controller: In a web application, the controller handles all the HTTP requests and sends an appropriate response. This response can mean rendering a template, outputting JSON data, and so on.
Note
For the exact definition, I suggest you check out the Wikipedia page of the MVC pattern at http...