Allowing a controller to access additional models through the $uses variable.
Model classes represent data and are used in CakePHP applications for data access. They generally represent a database table.
If model class is not defined then it uses AppModel and AppModel extend libray model class that describes :-
model classes represent data and are used in CakePHP applications for data access. They generally represent a database table but can be used to access anything that manipulates data such as files, external web services, or iCal events.