Скачать или смотреть Controllers and modules in AngularJS

Controller is a simple JavaScript function that is used to control the data of AngularJS application and increase the AngularJS scope. A controller is attached to the DOM object using ng-controller directive. When the controller is attached to the DOM, Angular instantiates the controller function and makes available an injectable parameter to the function called $scope.

Controller is used to

setup the initial state of the $scope object of that controller, in terms of setting up properties, objects, variables value etc.
attach behavior, specify function etc.
Controller is not used to
Format data
Filter data
Sharing between controllers
Manipulating DOM