Raspbmc is a full-fledged media center and offers the following capabilities:
Hardware playback of HD (up to 1080p) content in formats H264, MPEG2, and VC1, and MPEG2 and VC1 codecs must be purchased separately
Playback of multiple music formats (MP3, AAC, FLAC, and more)
Streaming content from a computer over a variety of streaming protocols
Support for different looks via skins
Streaming content from attached hard drives via USB
AirPlay support (with compatible iOS devices)
Watch and record TV on your device
Raspbmc can be controlled via a USB remote, a CEC-compatible device, or via a smartphone
Using various plugins, you can use online video and music services such as YouTube, Spotify, and iPlayer
Ability to create a media library that automatically downloads TV shows, film information, and FanArt
Ability to share this media library across multiple devices, including Windows, Linux, and Mac OSX systems
Automatic updating means that Raspbmc is always running at optimum performance and has the latest version of XBMC