Android OS vs. Android System

Android OS is based on Linux Kernel. It is low level kernel.
Android System is based on Android Platform. It is high level System.


Android System Arcitecture

+- Application Framework
+- Binder IPC Proxies
+- Android System Services (Media Server, System Server)
+- HAL
+- Linux Kernel

Android System controlls hardware with HAL interface. And HAL interface conncted with Linux Kernel. That is Android OS is Linux Kernel (low level kernel), Android System is Android platform.

1. http://forum.xda-developers.com/showpost.php?p=10922010&postcount=3
2. http://android.stackexchange.com/questions/11985/what-is-the-difference-between-the-android-os-and-android-system
3. https://source.android.com/devices/