Frameworks often use Inversion of Control, also known as the Hollywood "don't call us, we'll call you" style. For example the Struts framework accepts an incoming HTTP request, parses out the request parameters, maps the request to an action class and calls the action class, finally running code that you wrote.
Struts is in control. You can't change this sequence. Struts calls you when it's time for you to do something. Then it takes control again to call a view or something.
Here
Martin Fowler talks about how the inversion of control is what distinguishes a framework from a library.
Did that make sense? If you don't know Struts at all we can try again with a more familiar example.
[ August 25, 2006: Message edited by: Stan James ]