Is it possible to not describe some application components in the Manifest file?

Yes, it is possible.

Some components can be created dynamically in code and not explicitly registered in AndroidManifest.xml:

• Broadcast Receivers: Can be registered dynamically using Context.registerReceiver().
• Content Providers: Usually registered in the manifest, but in rare cases, an instance can be created programmatically and used, although this is not standard practice for public providers.
• Services: Registration in the manifest is mandatory for binding to the system's lifecycle.
• Activities: Registration in the manifest is mandatory for launching by the system.

Example of dynamic registration of a Broadcast Receiver:

// Dynamic registration of Broadcast Receiver
IntentFilter filter = new IntentFilter(ConnectivityManager.CONNECTIVITY_ACTION);
MyConnectivityReceiver receiver = new MyConnectivityReceiver();
registerReceiver(receiver, filter);

// Don't forget to unregister, for example, in OnPause() or OnDestroy()
// unregisterReceiver(receiver);