The AndroidManifest.xml file contains information of your package, including components of the application such as activities, services, broadcast receivers, content providers etc.
It performs some other tasks also:
It is responsible to protect the application to access any protected parts by providing the permissions.
It also declares the android api that the application is going to use.
It lists the instrumentation classes. The instrumentation classes provides profiling and other informations. These informations are removed just before the application is published etc.
This is the required xml file for all the android application and located inside the root directory.