Advanced Stream Redirector (ASX): 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 ASX file in a text editor and often find the filenames of the actual streaming content (often with an .asf extension denoting an ASF file).