This means with a single sub what ever the coil is is the load the amp will see. So if you have a SVC 4ohm sub your amp will see a 4ohm load
DVC = Dual Voice Coil
This means with a single sub you have 2 different ways of wiring the sub to best match your amps power output. With a DVC 4ohm sub you can wire it so you amp will see a 2ohm or 8ohm load