Simple we can say that angularJs binds the data to html using expressions this is called angularJs expressions.
AngularJs expression is written inside double braces such as {{your expresion}}
also you can write expression inside a directive such as ng-bind=”expression”.
AngularJs expression and javascript expression are similars the can contain literals,operators and variables.
example:
<!DOCTYPE html>
<html>
<script src=”https://ajax.googleapis.com/ajax/libs/angularjs/1.6.9/angular.min.js”></script>
<body>
<div ng-app=””>
<p>Test expression: {{ 2 + 2 }}</p>
</div>
</body>
</html>