ng-change event directive is fired when there is change in the input value or in other words whenever your HTML element changes ng-change is triggered.
ng-change syntax :
Lets see this event directive in action with some simple examples.
Example 1: Change in Checkbox element
So in this example we are incrementing the counter($scope.counter) whenever the checkbox is selected or unselected. The output gif would explain it much better.
Example 2 : Change in Dropdown element
In this example, we have invoked the counter incrementing function when the drop down element is changed
Hope these examples gives a good understanding on ng-change event directive in AngularJS.