Questions relating to Internet Information Server, the underlying web server software used to host Sitecore-based websites.
An IIS web server runs on the Microsoft .NET platform on the Windows OS. It's versatile and stable, and it's been widely used in production for many years. Version 10 is the most current which is used by Sitecore installation.
IIS is used to host ASP.NET web applications and static websites. It can also be used as an FTP server, host WCF services, and be extended to host web applications built on other platforms such as PHP.