An overview of Android components, and a diagram of the architecture are
available at Google's
[[http://developer.android.com/guide/basics/what-is-android.html |What is Android? page]]
The diagram on that page appears in every presentation I have ever seen regarding Android technical topics (with the exception of my own).
Here is the Android Architecture Diagram]
Breakdown of running Android system
A quick look at Android contents and programs running when Android starts is at: