iTunes is a digital media player application, introduced by Apple Inc. at the Macworld Expo in San Francisco. The application is used for playing and organizing digital music and video files. The program is also an interface to manage the contents on Apple's popular iPod digital media players as well as the iPhone. Additionally, iTunes can connect to the iTunes Store via the Internet to purchase and download music, music videos, television shows, iPod games, audiobooks, various podcasts, feature length films and Movie Rentals (available only in the USA, UK,Canada, Australia and New Zealand), and Ringtones (available only in the USA). Since July 11, 2008, there has also been the option to download apps for the iPhone and iPod Touch as long as they are running the 2.0 firmware released on the same date.
iTunes is available as a free download for Mac OS X, Windows Vista, and Windows XP from Apple's website. It is also bundled with all Macs, and some HP and Dell computers. Older versions are available for Mac OS 9, OS X 10.0-10.2, and Windows 2000. Although Apple does not produce iTunes for other operating systems, it can, however, be run on Linux-based operating systems through Wine, a Windows compatibility layer.
A version of iTunes shipped with cell phones from Motorola, which included the ability to sync music from an iTunes library to the cellphone, as well as a similar interface between both platforms. Since the release of the iPhone, Apple has stopped distributing iTunes with other manufacturers' phones in order to concentrate sales to Apple's device.
Source from Wikipedia.org