Model-View-Controller (MVC) is a widely used software architectural pattern that separates an application into three interconnected components: Model, View, and Controller. This separation promotes organized code, reusability, and scalability, particularly in web and desktop application development.

- Model: Represents the data layer of the application. It manages the business logic, rules, and the state of the application. For example, in an e-commerce app, the Model would handle products, prices, and user data.
- View: Refers to the presentation layer, which defines how the data should be displayed to the user. Views are typically composed of HTML, CSS, and UI frameworks that render the visual interface.
- Controller: Acts as an intermediary between the Model and the View. It receives user input from the View (like button clicks), processes it (often via the Model), and then updates the View accordingly.

One of the key advantages of MVC is separation of concerns, which allows developers to work on the user interface, business logic, and data separately. This leads to faster development cycles, better code maintenance, and easier testing.

A typical flow in an MVC application:
1. User interacts with the View (e.g., submits a form).
2. The Controller handles the input and updates the Model.
3. The Model modifies the data and notifies the View.
4. The View updates to reflect the new state of the Model.

MVC is implemented in many popular frameworks:
- Ruby on Rails (Ruby)
- ASP.NET MVC (C#/.NET)
- Django (Python – although it's technically MTV: Model-Template-View)
- Spring MVC (Java)

MVC mostly operates at the application layer of the OSI model and is part of the presentation and business logic tiers in multi-tier architectures.

In summary, Model-View-Controller (MVC) is a foundational design pattern that structures software applications in a modular and maintainable way. It enhances collaboration across teams and supports clean, testable code in both frontend and backend development.