See the entire IIS Architecture and components tutorial at :

In part two of the video series I explore the inner workings of the worker process – w3wp.exe – which is the process that loads and executes the code for the web-applications hosted under IIS. I also look at the differences between classic mode pipeline execution and integrated mode pipeline execution.

Don't forget to have a look at the first video of the series that deals with the general architecture of IIS. You can view the video here:

By Paul Cociuba