What is the functionality of Window in Android Graphics?

Question

While going throigh the material available online on Android Graphics, I have few queries related to Android Graphics:

1. What is Window ? how it is related to View ?
2. Does every application have its own Window ?
3. Can one application have more than one window ?
4. As Surfaceflinger composes surface does it composes the window also ?

I have gone through other question asked also, but still these question is not clear to me.