title: Android framework. What is it?
body: <p>I've few questions on Android Framework. Can someone please answer 
  them </p>
  
  <ol>
  <li><p>What does an Android Framework
  do? What is it's job? </p></li>
  <li><p>What are these managers -
  Activity Manager, Location Manager
  etc?  Are they APIs or libraries? </p></li>
  <li><p>I heard that the definition of
  a framework is - a set of  libraries
  that say “Don’t call us, we’ll call
  you.”  So can I say that  Activity
  Manager, Location Manager etc are
  such libraries? Or is it  that they
  are not libraries but APIs (used to
  access underlying c/c++  libraries)
  and the actual libraries that do
  "Don't call us, we'll call  you."
  are hidden from us?</p></li>
  </ol>