What is the Difference between Apache and IIS

Apache	IIS
Apache is free.	IIS is packaged with Windows.
Apache can run on almost any OS including UNIX, Apple’s OS X, and on most Linux Distributions.	IIS only runs on Windows.
Apache comes from the community itself.	IIS has a dedicated staff to answer most problems while support.
Apache optimized for the most of the OS including UNIX, Apple's OS X, Linux.	IIS is optimized for Windows because they are from the same company.
The original Apache web server is based upon HTTP code largely credited for revolutionizing the entire World Wide Web. As an open-source software product, the earlier days saw it being used to mainly work with Unix and Unix-like platforms, even though it could be tweaked to work within the Windows environment.	Since Windows NT 4.0 launched, Microsoft IIS has been available as an optional feature on Windows Server operating systems. At the time, IIS 3.0, was a basic application and didn’t really get its push as a true platform until IIS 4.0. The Microsoft server took off with the release of Windows Server 2003 and IIS 6.0, which was far more superior to previous editions. With the recent release of Windows Server 2008, IIS 7.0 was introduced, unleashing power and performance that would make it one of the most effective web servers on the market.