XBMC is a free and open-source media player software that runs on multiple platforms including Linux, Mac OS X, iOS, and Windows. It allows users to play video, music, and photos from local storage devices, network shares, and online services. Key features include support for 1080p playback acceleration, media library organization with metadata grabbing from IMDB, support for DVDs and Blu-rays with menus, and multiple audio streams and subtitles. Addons and skins allow users to customize and expand XBMC's functionality further.