plays songs in a shuffle mode through the whole playlist. The track enumeration will show the currently playing track number. When switched off, the playback will continue from the currently playing track.
when turned on, it will play the first track in the playlist after the last track is played. If switched off, the playback will continue to the next playlist once the current one has played the last song.
on some stereos, this button will switch over to show the disk or artist of the current track playing.