ASX

The Advanced Stream Redirector (ASX) format is a type of XML metafile designed to store a list of Windows Media files to play during a multimedia presentation

When you use .asx files, you are directed to streaming media content, usually on multimedia Web sites. The .asx files are simple text files that contain server and media information. They are metafiles (a file that provides information about Windows Media files and their presentation) that are similar to Windows Media Redirector (.wvx) files.

If you want to find out more about the streaming content you can open an Advanced Stream Redirector file in a text editor and often find the filenames of the actual streaming content (often with an .asf extension denoting an Advanced Streaming Format file).