Internet Information Services (IIS, formerly Internet Information Server) is an extensible web server created by Microsoft for use with Windows NT family. IIS supports HTTP, HTTPS, FTP, FTPS, SMTP and NNTP. It has been an integral part of the Windows NT family since Windows NT 4.0, though it may be absent from some editions (e.g. Windows XP Home edition). IIS is not turned on by default when Windows is installed. The IIS Manager is accessed through the Microsoft Management Console or Administrative Tools in the Control Panel. Internet Information Services (IIS), formerly known as Internet Information Server, is a web server producted by Microsoft. IIS is used with Microsoft Windows OSs and is the Microsoft-centric competition to Apache, the most popular webserver used with Unix/Linux-based systems.
This changed with later releases, and IIS is now generally considered by many to be a stable and usable product. As of 2011, the most current version is IIS 7, which includes pretty much all modern features you'd expect to see in a webserver, including tight integration to ASP.NET. Though, as with any Microsoft vs Linux debate, some would argue that Apache is the only way to go.