XMMS2 is an audio framework, but it is not a general multimedia player - it will not play videos.
It has a modular framework and plugin architecture for audio processing, visualisation and output, but this framework has not been designed to support video.
Also the client-server design of XMMS2 (and the daemon being independent of any graphics output) practically prevents direct video output being implemented.
It has support for a wide range of audio formats, which is expandable via plugins.
It includes a basic CLI interface to the XMMS2 framework, but most users will want to install a graphical XMMS2 client (such as gxmms2 or esperanza).
