Rack Usage

Hi,

I have started exploring on Rack. But still, I am not able to find the exact usage of the 'Rack'. I want to create a sample application with Rack. Can anybody guide me in this? Can you explain the advantage of the Rack? And can you provide some links for the Rack tutorial?

Thanks in advance...

http://www.google.com/search?client=safari&rls=en-us&q=ruby+rack&ie=UTF-8&oe=UTF-8

Best regards

Peter De Berdt