Kodi (formerly known as XBMC) is a multimedia center suitable to build home-theater PCs (HTPCs). Kodi contains special support for the RPi hardware but it has to be enabled during compilation. RPiBuntu provides such a special build and the necessary dependencies.
You can install kodi with
apt-get install kodi. If you want to start kodi at
startup automatically, install
kodi-desktop. This installs additional
dependencies, e.g., upower in order to shut the RPi down from the Kodi menu.