If you don't know how each ASP.NET request is processed then you are lacking a vital piece of knowledge. The HttpApplication is usually un-heard of and it works quietly behind the scenes - well not really. If you have written a HttpHandler or HttpModule or any application with some sort of complexity before - you probably already know what its all about. The HttpApplication is the base class for all ASP.NET application objects, therefore, an HttpApplication class is created for each request.
As famous as the word generics is among .Net developers, I was amazed when I found out that a huge percentage of .Net developers have only heard of it but have never actually used it or know of any reason why they should use it. If you have read my past articles, you would know that my philosophy is to code simple and efficiently, there is no need to write complex code that could have been done with simple techniques.