Bootstrapping is the equivalent of initializing, or starting, your Angular app. There are 2 main ways to do so.
The first is automatically bootstrapping by adding ng-app to the an element in your HTML, like so:
<html ng-app="myApp">
...
</html>
The second would be to bootstrap from the JavaScript, like so, after having creating your app through angular.module("myApp", []);
angular.bootstrap(document, ['myApp']);