What is ng-binding for in AngularJS?

I am an AngularJS newbie and trying to figure out what class=ng-binding does in this example:

<label ng-dblclick="editTodo(todo)" class="ng-binding">fghfgh</label>

I found it here:

http://todomvc.com/architecture-examples/angularjs/#/

I use Chrome and developer tools. Is this an angular keyword? I could not find it in the manual (http://docs.angularjs.org/api/ng.directive:ngBind)