App models classes are responsible for managing almost everything that happens regarding data, its validity, interactions and evolution of the information workflow in a CakePHP project.

Usually model classes represent data and are used in CakePHP applications for data access, more specifically they represent a database table but they are not limited to this, but can be used to access anything that manipulates data such as files, external web services, iCal events, or rows in a CSV file.

Source: Manual Reference

Example: (CakePHP 2.x)

App::uses('AppModel', 'Model');
class Ingredient extends AppModel {
    public $name = 'Ingredient';
}