Controller

AngularJS applications are controlled by Controller. AngularJS controllers are used for control the data of AngularJS applications. AngularJS controllers are regular JavaScript Objects.
For define controller in AngularJS application we need ng-controller directive names

Example

<!DOCTYPE html>
<html>
<head>
<script src= "http://ajax.googleapis.com/ajax/libs/angularjs/1.2.26/angular.min.js"></script>
</head>
<body>

<div ng-app="" ng-controller="AJSController">

First Name: <input type="text" ng-model="firstName"><br>
Last Name: <input type="text" ng-model="lastName"><br>
<br>
Full Name: {{firstName + " " + lastName}}

</div>

<script>
function AJSController($scope) {
    $scope.firstName = "Harry",
    $scope.lastName = "Porter"
}
</script>

</body>
</html>

Result

First Name: 
Last Name: 

Full Name: Harry Porter
In above example controller are use for conrtoller firstName and lastName. AngularJS will invoke personController with a $scope object.