Here you can choose to repeat a song after playing it or go on to play the next song in the Music Desktop's list.  You can also specify if you want to play songs in stereo and surround sound.  If you computer does not support stereo, these two items will be dimmed.  Other features such as reverb and stereo delay also alter the way songs play.  The playback rate affects the quality of the song playing.  It also affects the speed of your computer.  On slower machines, 44kHz playback may cause your computer to seem sluggish.