IIS is a web server that runs on Windows only, whereas Apache is a cross-platform server that will work on Windows, Linux, Mac OS X and various flavors of UNIX. Though you can make either of these servers work with pretty much any web technology (ASP.NET, PHP, Python) there are some natural pairings that you'll find are pretty common.
If you're working with ASP.NET, IIS is the natural fit since both are Microsoft products. Learning how to work with it will help you if you were to start placing your applications on IIS servers later on.
PHP and Python are more naturally paired with Apache. XAMPP, for example, already comes with PHP configured to work on Apache. (LAMP, WAMP and MAMP are other editions of this on various platforms.