Internet Information Services (IIS) is a real, full-featured Web server. IIS is "real" by comparison to the Visual Studio Web server used for development because:
You can access the Web pages served by IIS from any machine connected to the Web server running IIS. The Visual Studio Web server can be accessed only on the machine on which it is running.
IIS virtually always runs on the standard HTTP and HTTPS ports, whereas the Visual Studio Web server always runs on a randomly assigned port.
IIS can be installed on Windows 2000 Professional, Windows 2000 Server, Windows XP Professional, and Windows Server 2003. IIS cannot be installed on any home edition of Windows. Windows 2000 (all editions) installs IIS by default, which has created many machines with a running Web server and no one looking at the security implications of doing so. IIS is not installed by default on any operating system later than Windows 2000.
IIS can be installed from the Control Panel by opening Add Or Remove Programs. In the Add Or Remove Programs dialog box, click Add/Remove Windows Components. In the Windows Components Wizard dialog box, you can select Internet Information Services (IIS) and simply click Next. Or, if you want to view details of the IIS components being installed, you can click Details and select the specific portions of IIS that you want to install. To deploy an ASP.NET application, you must ensure that the World Wide Web service is installed, because this is the portion of IIS required for ASP.NET applications.
Appendix A contains more details on moving your Web Forms application to IIS.