When using certain directives, Angular attaches additional (unnecessary) debug information to the elements they are applied to. When we use interpolation or data-binding directives to evaluate an expression, Angular adds an additional ng-binding class to the directive’s, or directive’s parent element. Say we have a scope property like this: app.controller(‘AppController’, [‘$scope’, function ($scope) { $scope.name = ‘Troy’; }]); And we have an expression in our HTML code like this: <p>Hello {{name}}!