what is MVC? why its been used?

Model-view-controller (MVC) is an architectural pattern used in software engineering. Successful use of the pattern isolates business logic from user interface considerations, resulting in an application where it is easier to modify either the visual appearance of the application or the underlying business rules without affecting the other. In MVC, the model represents the information (the data) of the application; the view corresponds to elements of the user interface such as text, checkbox items, and so forth; and the controller manages the communication of data and the business rules used to manipulate the data to and from the model.

WHY ITS NEEDED IS
1 Modular separation of function
2 Easier to maintain
3 View-Controller separation means:
A — Tweaking design (HTML) without altering code B — Web design staff can modify UI without understanding code.