1.1. Introducing IIS
It helps to relate IIS—and web servers in general—to something you already know. In most cases IIS performs the same job as a file server, serving web pages as files to a network client across the internet. The client uses a browser that displays and runs those files as a useful application.
The same concerns you have about file servers regarding security and performance still apply, and in many cases IIS is configured similarly. But there is much more to IIS and its architecture, mainly due to the security challenges that impact any server connected to the internet and the need to be able to run many different types of web applications.
Figure 1.1 is a simple description of how IIS works. It provides a good starting point ...