HTTP request dispatch from Web Server to a CGI/FastCGI process

To gain more understanding of how HTTP requests are handled in case of web apps, how does a web server like Apache, dispatch a request to one of its Virtual Hosts? What are the initial programs executed irrespective of the framework (Rails/PHP/Java)? I would appreciate if someone can list the steps taking example of Rails (as I know Rails). Thanks in advance!

From stackoverflow

• Ah, couple of good rails specific articles that explain most of what I wanted wanted to know:

  http://railsguts.com/initialization.html

  http://www.codeweblog.com/rails-startup-process/