Functionality of the key files in .net application

AssemblyInfo.cs
An information file that provides the compiler with metadata (name, version, etc.) about the assemblies in the project.

Global.asax
Customizable to handle application-level events (e.g., Application_OnStart).

HelloWorldService.vsdisco (HelloWorldService is the name of a webservice)
An XML file used for dynamic discovery of web services.

Web.config
An XML file containing configuration information for the application.