- Model: a class that describes the what or thing being modelled.
- View: a class that provides a user with a way of interacting with the thing being modelled; it both shows a representation of the model and (possibly) allows the user to make changes to the model. Multiple different views may simultaneously offer different representations of the same underlying model object.
- Controller: a class that mediates between the model and its view or views.
The key benefits of applying the MVC approach stem from maintaining a separation of concerns; this in turn leads to greater readability, modularity and maintainability. It also helps break the design into segments that can be independently tested (see "Independently testing models, views and controllers").
Examples of popular systems that are designed to use the MVC pattern include: