Its a marker on a html tag that tells Angular to run or reference some javascript code. This is used to bind the behavior. These are HTML annotation that triggers javascript behaviors.
eg:
<body ng-controller="StoreController">
....
</body>
function StoreController() {
}
Mini - components and separation of concerns inside an application.
<html ng-app="store"> </html>
var app = angular.module("store", []);
Allows you to insert dynamic values into HTML. Decides how data gets displayed on website.
<p>{{ data }} </p>
Application behavior is added here.
app.controler("controllerName", function(){});
Allows to format the output.
<p> {{ data | filter:options }} </p>