It’s a built-in media player on Windows, which supports playing videos, audio files, and viewing images. The first ASF player you can use is Windows Media Player.
If you have some ASF videos on your PC and want to play them without buffering, don’t worry, this post lists 5 best free ASF players out there (Want to extract MP3 from a video? Try MiniTool MovieMaker). It’s a container format that stores audio, video, images, URLs, and scripts, which is designed to stream media online.