PLS is a playlist file that you can use to play your favorite soundtracks on the go. However, it doesn't contain the actual audio, but it stores references or links to open and play audio files in a supported media player. It can be used locally as well as for streaming music playlists online. The online media servers use PLS playlists to stream audio on the web. You can also download a PLS file from an online radio or some other source to stream and play music playlists on their device.