Output impedance CD/DVD Players

I'm trying to better understand the spec called "output impedance" on CD and DVD players. I've read the definitions and have talked about it with others but I still don't grasp it fully. Why is it desirable for a CD/DVD player to have a low output impedance? Does it mean that the lower the output impedance, the louder it will play (in dB's)at the same volume setting on the amp than another CDP will produce with a higher output impedance? Does that make sense? Please explain. Thanks.