What does it mean when something "drops voltage"?
If you have a water supply and the pressure drops (due to a long small-bore pipe) then this is the same as a volt-drop but in the world of hydraulics. The pressure may be good at the feed end of the pipe but at the far end of the pipe (with a certain flow of water aka current) the pressure has dropped.

The pipe acts the same as a electrical resistor - it drops pressure just as the resistor drops voltage.