The Advanced Systems Format (ASF) is the file format used by Windows Media. Audio and/or Video content compressed with a wide variety of codecs can be stored in an ASF file and played back with the Windows Media Player (provided the appropriate codecs are installed), streamed with Windows Media Services or optionally packaged with Windows Media Rights Manager.
ASF is an extensible file format designed to store synchronized multimedia data. It supports data delivery over a wide variety of networks and protocols while still proving suitable for local playback. ASF supports advanced multimedia capabilities including extensible media types, component download, scaleable media