Internet Explorer has been available on other Operating Systems in past versions but the last 3 versions have only been for the Microsoft Windows OS
There are multiple versions of this Browser. Most commonly right now you will come across:
Was released on August 27, 2001, a few months before Windows XP and has been the most common Browser for a few years now.
The end-of-life support for Internet Explorer 6 is July 13, 2010
Was released on October 18, 2006. Comes standard with Windows Vista and Windows 7.
Was released on March 19, 2009. Is currently in Beta, doesn't work so good.