Internet Information Services. That's Microsoft's universal web server. It's what all Windows-based systems run for a web server (well, you can load Apache onto Windows...but IIS is the default). It comes in slightly different "flavors", depending on what version of Windows you are using. As I mentioned, on Home Premium it only supports a single web site, whereas on Windows Server (even Windows Small Business Server) it will support dozens or more web sites. I know one system I work on with Small Business Server supports 22 different IP Addresses, for example (more than that number of web sites, because [for example] we have both ".com" and ".net" pointed to the same IP address for all).
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.