After reading the HTML which is there within the root, Angular compiles it all into an internal representation. This process of reading and compiling is called as the bootstrapping process. When the code is written instead of the use of the ng-app directive, manual bootstrapping is done. It is actually the functional component that is there in the Core ng module which is actually used so that the user can start up an application hosted by Angular manually. Thereby it provides more control over the beginning of the application.